Minecraft Forums

Today I downloaded the 1.8.9 version of the Thaumcraft mod from the curse website. I placed the download into the mods folder and created a new profile to run it. It appeared to load, but then suddenly crashed. I'm not sure what the issue is, and therefore cannot fix it. Any insight would be appreciated.

What does the crash page look like? also do you have any other mods running?

No, Thaumcraft is the only mod I have. Here's a copy of the crash report:

---- Minecraft Crash Report ----

WARNING: coremods are present:
ThaumcraftLoader (Thaumcraft-1.8.9-5.2.4.jar)
Contact their authors BEFORE contacting forge

// I bet Cylons wouldn't have this problem.

Time: 10/6/16 9:50 AM
Description: Initializing game

java.lang.NoClassDefFoundError: bxf
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2575)
at java.lang.Class.getField0(Class.java:2967)
at java.lang.Class.getField(Class.java:1693)
at net.minecraftforge.fml.client.FMLClientHandler.detectOptifine(FMLClientHandler.java:277)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:191)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:417)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:329)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.ClassNotFoundException: bxf
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 15 more
Caused by: java.lang.NullPointerException
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182)
... 17 more


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2575)
at java.lang.Class.getField0(Class.java:2967)
at java.lang.Class.getField(Class.java:1693)
at net.minecraftforge.fml.client.FMLClientHandler.detectOptifine(FMLClientHandler.java:277)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:191)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:417)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:329)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.8.9
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 63440632 bytes (60 MB) / 315621376 bytes (301 MB) up to 1908932608 bytes (1820 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx2G
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML:
Loaded coremods (and transformers):
ThaumcraftLoader (Thaumcraft-1.8.9-5.2.4.jar)

Launched Version: 1.8.9-forge1.8.9-11.15.1.1722
LWJGL: 2.9.4
OpenGL: Intel(R) HD Graphics 5500 GL version 4.4.0 - Build 20.19.15.4444, Intel
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: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs:
Current Language: ~~ERROR~~ NullPointerException: null
Profiler Position: N/A (disabled)
CPU: 4x Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz

I've dealt with this before and it used to be such a pain, but your case seems a bit different, it looks like the mod hadn't even been unpackaged yet. First I suggest checking your forge, mod, and game versions and make sure they're all the same. And if you can't find the source of the error, then download the mod without an installer and just drag and drop the .jar. I use Thaumcraft 4 on 1.7.10 problem free, if all else fails you could use that.

I downloaded forge for 1.7.10 and attempted to run it on the launcher, but ended up crashing again.

Ok, I downloaded it for 1.7.10 and it ended up working! Thank you so much for the help