So I went onto my computer because I felt like playing some Lucky Block Survival (my own little games using lucky blocks). So I loaded the minecraft client (I have version 1.6.11) and clicked the 1.7.2 Forge profile and I clicked Play, but it didnt load and came up with this:

[b][b][19:06:28] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[19:06:28] [main/INFO] [LaunchWrapper]: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[19:06:28] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker
[19:06:28] [main/INFO] [FML]: Forge Mod Loader version 7.2.207.1110 for Minecraft 1.7.2 loading
[19:06:28] [main/INFO] [FML]: Java is Java HotSpot(TM) Client VM, version 1.8.0_31, running on Windows 7:x86:6.1, installed at C:\Program Files (x86)\Java\jre1.8.0_31
[19:06:28] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[19:06:28] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker
[19:06:28] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[19:06:28] [main/ERROR] [LaunchWrapper]: Unable to launch
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source) ~[?:1.8.0_31]
at java.util.ArrayList$Itr.remove(Unknown Source) ~[?:1.8.0_31]
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(TM) Client VM warning: Using incremental CMS is deprecated and will likely be removed in a future release

It is the same with my 1.6.4 Forge. Game output:

Feb 25, 2015 7:13:49 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
Feb 25, 2015 7:13:50 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker
Feb 25, 2015 7:13:50 PM net.minecraft.launchwrapper.LogWrapper log
INFO: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker
2015-02-25 19:13:50 [INFO] [ForgeModLoader] Forge Mod Loader version 6.4.49.965 for Minecraft 1.6.4 loading
2015-02-25 19:13:50 [INFO] [ForgeModLoader] Java is Java HotSpot(TM) Client VM, version 1.8.0_31, running on Windows 7:x86:6.1, installed at C:\Program Files (x86)\Java\jre1.8.0_31
2015-02-25 19:13:50 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
2015-02-25 19:13:50 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker
2015-02-25 19:13:50 [INFO] [ForgeModLoader] Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
2015-02-25 19:13:50 [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

It usually works with no lag. The mods I have (which all work together) are:
Lucky Blocks
Orespawn
Zan's Minimap
Damage Indicators

Please help!