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Jan 12, 2015 8:34:00 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
Jan 12, 2015 8:34:01 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker
Jan 12, 2015 8:34:01 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker
2015-01-12 20:34:01 [INFO] [ForgeModLoader] Forge Mod Loader version 6.4.49.965 for Minecraft 1.6.4 loading
2015-01-12 20:34:01 [INFO] [ForgeModLoader] Java is Java HotSpot(TM) Client VM, version 1.8.0_25, running on Windows 8.1:x86:6.3, installed at C:\Program Files (x86)\Java\jre1.8.0_25
2015-01-12 20:34:01 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
2015-01-12 20:34:01 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker
2015-01-12 20:34:01 [INFO] [ForgeModLoader] Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
2015-01-12 20:34:01 [SEVERE] [ForgeModLoader] Unable to launch
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
at java.util.ArrayList$Itr.remove(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:114)
at net.minecraft.launchwrapper.Launch.main(Launch.java:27)
Java HotSpot(TM) Client VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

http://www.reddit.com/r/feedthebeast/comments/2fe3sa/psa_java_8_update_20_and_later_is_incompatible/



You can get the Coremod here and toss in Mods folder and it will patch the problem. Future forge builds, including old forge builds, already have this fix applied. This coremod is just so you do not have to mess with your modpack which could break something.

Thanks. Seems to be working for the most part. (Still wish I could actually play the game at more than 5-15 FPS.)