I'm having an issue, where when i hit the 'play' button the launcher closes but the game won't open. i even set it to not close the laucher, because it wouldn't re-open with an error report.  
  
Logs:[02:20:05] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker 
[02:20:05] [main/INFO] [LaunchWrapper]: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker 
[02:20:05] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker 
[02:20:05] [main/INFO] [FML]: Forge Mod Loader version 7.10.18.1180 for Minecraft 1.7.10 loading 
[02:20:05] [main/INFO] [FML]: Java is Java HotSpot 64-Bit Server VM, version 1.8.0_20, running on Windows 8:amd64:6.2, installed at C:\Program Files\Java\jre1.8.0_20 
[02:20:05] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker 
[02:20:05] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker 
[02:20:05] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker 
[02:20:05] [main/ERROR] [LaunchWrapper]: Unable to launch 
java.util.ConcurrentModificationException 
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source) ~[?:1.8.0_20] 
	at java.util.ArrayList$Itr.remove(Unknown Source) ~[?:1.8.0_20] 
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:117) [launchwrapper-1.9.jar:?] 
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.9.jar:?] 
Java HotSpot 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release 
  
i have no mods that use FORGE.