Gulliver not launching.

Wont launch and I'm unsure why, if anyone could help here's the error message:

Apr 24, 2016 9:20:35 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
Apr 24, 2016 9:20:35 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker
Apr 24, 2016 9:20:35 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker
2016-04-24 21:20:35 [INFO] [ForgeModLoader] Forge Mod Loader version 6.4.49.965 for Minecraft 1.6.4 loading
2016-04-24 21:20:35 [INFO] [ForgeModLoader] Java is Java HotSpot(TM) 64-Bit Server VM, version 1.8.0_25, running on Windows 10:amd64:10.0, installed at C:\Program Files (x86)\Minecraft\runtime\jre-x64\1.8.0_25
2016-04-24 21:20:35 [SEVERE] [ForgeModLoader] The coremod de.sanandrew.core.manpack.init.ManPackLoadingPlugin is requesting minecraft version 1.7.10 and minecraft is 1.6.4. It will be ignored.
2016-04-24 21:20:35 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
2016-04-24 21:20:35 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker
2016-04-24 21:20:35 [INFO] [ForgeModLoader] Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
2016-04-24 21:20:35 [SEVERE] [ForgeModLoader] Unable to launch
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
at java.util.ArrayList$Itr.remove(ArrayList.java:865)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:114)
at net.minecraft.launchwrapper.Launch.main(Launch.java:27)
Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

Well, I took the legacy java fixer out of my mods and my crash report is nearly identical to yours. I'm guessing you didn't check the support tickets thread before making this.

To fix this, just put this: http://files.minecraftforge.net/LegacyJavaFixer/legacyjavafixer-1.0.jar in your mods folder and try reopening gulliver.

Also, this type of thread belongs in the support tickets, not here, for future reference.

sorry, and thanks.