java.lang.IllegalStateException: failed to create a child event loop
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:88)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47)
at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:58)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:77)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:72)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:59)
at oz$1.a(SourceFile:61)
at oz$1.b(SourceFile:58)
at rh.c(SourceFile:10)
at oz.a(SourceFile:152)
at bib.a(SourceFile:2209)
at bol.e(SourceFile:229)
at bol.a(SourceFile:182)
at bol.a(SourceFile:148)
at bjm.a(SourceFile:41)
at bok.a(SourceFile:117)
at blk.k(SourceFile:400)
at bok.k(SourceFile:49)
at blk.q(SourceFile:377)
at bib.t(SourceFile:1625)
at bib.az(SourceFile:1000)
at bib.a(SourceFile:419)
at net.minecraft.client.main.Main.main(SourceFile:123)
Caused by: io.netty.channel.ChannelException: failed to open a new selector
at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:157)
at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:149)
at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:127)
at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:36)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:84)
... 23 more
Caused by: java.io.IOException: Unable to establish loopback connection
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:101)
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:68)
at java.security.AccessController.doPrivileged(Native Method)
at sun.nio.ch.PipeImpl.<init>(PipeImpl.java:170)
at sun.nio.ch.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:50)
at java.nio.channels.Pipe.open(Pipe.java:155)
at sun.nio.ch.WindowsSelectorImpl.<init>(WindowsSelectorImpl.java:127)
at sun.nio.ch.WindowsSelectorProvider.openSelector(WindowsSelectorProvider.java:44)
at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:155)
... 27 more
Caused by: java.net.ConnectException: Connection refused: connect
at sun.nio.ch.Net.connect0(Native Method)
at sun.nio.ch.Net.connect(Net.java:457)
at sun.nio.ch.Net.connect(Net.java:449)
at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:647)
at java.nio.channels.SocketChannel.open(SocketChannel.java:189)
at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(PipeImpl.java:130)
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:83)
... 35 more
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- Head --
Thread: Client thread
Stacktrace:
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:88)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47)
at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:58)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:77)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:72)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:59)
at oz$1.a(SourceFile:61)
at oz$1.b(SourceFile:58)
at rh.c(SourceFile:10)
at oz.a(SourceFile:152)
at bib.a(SourceFile:2209)
at bol.e(SourceFile:229)
at bol.a(SourceFile:182)
at bol.a(SourceFile:148)
at bjm.a(SourceFile:41)
at bok.a(SourceFile:117)
at blk.k(SourceFile:400)
at bok.k(SourceFile:49)
at blk.q(SourceFile:377)
-- Affected screen --
Details:
Screen name: bli
Stacktrace:
at bib.t(SourceFile:1625)
at bib.az(SourceFile:1000)
at bib.a(SourceFile:419)
at net.minecraft.client.main.Main.main(SourceFile:123)
-- System Details --
Details:
Minecraft Version: 1.12.1
Operating System: Windows Vista (x86) version 6.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 172245192 bytes (164 MB) / 293859328 bytes (280 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Launched Version: 1.12.1
LWJGL: 2.9.4
OpenGL: GeForce GT 730/PCIe/SSE2 GL version 4.5.0 NVIDIA 359.06, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.
Using VBOs: Yes
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs:
Current Language: English (US)
Profiler Position: N/A (disabled)
CPU: 2x Pentium(R) Dual-Core CPU E5300 @ 2.60GHz
Is there any indication of which program is the problem in the error log?
I have a feeling it is Avast interfering with it, or possibly GeForce Experience, since that is the only thing on the list. :/
The odd thing is it was literally working fine the day before this started happening. :/
Will post what I did to fix it or if the problem still persists in a day or so.
First forgive me if this is in the wrong thread, as I did not see a bug thread under vanilla minecraft.

Second, whenever I load a world minecraft crashes.
I have done all the obvious things to try and fix it, so I turn to you all for help.
Thank you for your time, and any help provided.
---- Minecraft Crash Report ----
// Everything's going to plan. No, really, that was supposed to happen.
Time: 9/13/17 6:33 PM
Description: Updating screen events
java.lang.IllegalStateException: failed to create a child event loop
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:88)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47)
at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:58)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:77)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:72)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:59)
at oz$1.a(SourceFile:61)
at oz$1.b(SourceFile:58)
at rh.c(SourceFile:10)
at oz.a(SourceFile:152)
at bib.a(SourceFile:2209)
at bol.e(SourceFile:229)
at bol.a(SourceFile:182)
at bol.a(SourceFile:148)
at bjm.a(SourceFile:41)
at bok.a(SourceFile:117)
at blk.k(SourceFile:400)
at bok.k(SourceFile:49)
at blk.q(SourceFile:377)
at bib.t(SourceFile:1625)
at bib.az(SourceFile:1000)
at bib.a(SourceFile:419)
at net.minecraft.client.main.Main.main(SourceFile:123)
Caused by: io.netty.channel.ChannelException: failed to open a new selector
at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:157)
at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:149)
at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:127)
at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:36)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:84)
... 23 more
Caused by: java.io.IOException: Unable to establish loopback connection
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:101)
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:68)
at java.security.AccessController.doPrivileged(Native Method)
at sun.nio.ch.PipeImpl.<init>(PipeImpl.java:170)
at sun.nio.ch.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:50)
at java.nio.channels.Pipe.open(Pipe.java:155)
at sun.nio.ch.WindowsSelectorImpl.<init>(WindowsSelectorImpl.java:127)
at sun.nio.ch.WindowsSelectorProvider.openSelector(WindowsSelectorProvider.java:44)
at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:155)
... 27 more
Caused by: java.net.ConnectException: Connection refused: connect
at sun.nio.ch.Net.connect0(Native Method)
at sun.nio.ch.Net.connect(Net.java:457)
at sun.nio.ch.Net.connect(Net.java:449)
at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:647)
at java.nio.channels.SocketChannel.open(SocketChannel.java:189)
at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(PipeImpl.java:130)
at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:83)
... 35 more
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- Head --
Thread: Client thread
Stacktrace:
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:88)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58)
at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47)
at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:58)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:77)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:72)
at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:59)
at oz$1.a(SourceFile:61)
at oz$1.b(SourceFile:58)
at rh.c(SourceFile:10)
at oz.a(SourceFile:152)
at bib.a(SourceFile:2209)
at bol.e(SourceFile:229)
at bol.a(SourceFile:182)
at bol.a(SourceFile:148)
at bjm.a(SourceFile:41)
at bok.a(SourceFile:117)
at blk.k(SourceFile:400)
at bok.k(SourceFile:49)
at blk.q(SourceFile:377)
-- Affected screen --
Details:
Screen name: bli
Stacktrace:
at bib.t(SourceFile:1625)
at bib.az(SourceFile:1000)
at bib.a(SourceFile:419)
at net.minecraft.client.main.Main.main(SourceFile:123)
-- System Details --
Details:
Minecraft Version: 1.12.1
Operating System: Windows Vista (x86) version 6.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 172245192 bytes (164 MB) / 293859328 bytes (280 MB) up to 523501568 bytes (499 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
Launched Version: 1.12.1
LWJGL: 2.9.4
OpenGL: GeForce GT 730/PCIe/SSE2 GL version 4.5.0 NVIDIA 359.06, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.
Using VBOs: Yes
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs:
Current Language: English (US)
Profiler Position: N/A (disabled)
CPU: 2x Pentium(R) Dual-Core CPU E5300 @ 2.60GHz
Some program is blocking MC, check list in the FAQ here http://www.minecraftforum.net/forums/support/unmodified-minecraft-client/2827415-1-12-faqs-read-before-posting
Thank, for the quick reply.


Is there any indication of which program is the problem in the error log?
I have a feeling it is Avast interfering with it, or possibly GeForce Experience, since that is the only thing on the list. :/
The odd thing is it was literally working fine the day before this started happening. :/
Will post what I did to fix it or if the problem still persists in a day or so.
Thank you again for the response.
Ok so Avast added Java to the block list, heck if I know why. :/

All that was needed to fix it was remove java from the block list.
Thanks again for the quick reply.