Minecraft closes after selecting forge profile

[TomNorton42]

When I select the forge profile (using 1.6.4 as I'm trying to get crazycraft to work) and press play minecraft closes for no apparent reason and no error messages appear. Minecraft opens normally with my account and I am using the latest version of forge for 1.6.4. If I keep the launcher open this message appears under the log:

Sep 13, 2014 6:30:09 PM net.minecraft.launchwrapper.LogWrapper log

INFO: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker

Sep 13, 2014 6:30:09 PM net.minecraft.launchwrapper.LogWrapper log

INFO: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker

Sep 13, 2014 6:30:09 PM net.minecraft.launchwrapper.LogWrapper log

INFO: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker

2014-09-13 18:30:10 [iNFO] [ForgeModLoader] Forge Mod Loader version 6.4.49.965 for Minecraft 1.6.4 loading

2014-09-13 18:30:10 [iNFO] [ForgeModLoader] Java is Java HotSpot 64-Bit Server VM, version 1.8.0_20, running on Windows 8.1:amd64:6.3, installed at C:\Program Files\Java\jre1.8.0_20

2014-09-13 18:30:10 [iNFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

2014-09-13 18:30:10 [iNFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker

2014-09-13 18:30:10 [iNFO] [ForgeModLoader] Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

2014-09-13 18:30:10 [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 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

I have tried using both java runtime environment 7 and 8 and am not sure what to do

[TomNorton42]

I have done it with java 7 and the same thing happens

[TomNorton42]

I have completely uninstalled java 8, i only have java 7 on my pc and that is the log i get

[TomNorton42]

found java 8 on my recovery disc but the problem is still not solved, now minecraft won't boot. Error message says the registry refers to a non existent JRE or the runtime is corrupted

[TomNorton42]

seems to have worked after a little bit of playing around with all my drives to locate any remnants of java 8,

cheers for the help