First time using forge outside of FTB, I'm trying to mod vanilla. I've read through the EAQ and the recommendation for the error I'm having (forge not launching minecraft) is to update forge. But I want to run 1.7.2 mostly because the mods I want are only updated so far.

 

There's probably something really simple I'm missing here, but, how are people supposed to play older mods in this case? I *did* run forge for 1.8 and minecraft launched. Deleted .minecraft folder. Ran latest 1.7.2 build and started having this problem. Deleted .minecraft and tried it with recommended 1.7.2 build; same thing.

 

Anyway here's the log:

 

[23:45:45] [main/INFO] [FML/]: Forge Mod Loader version 7.2.211.1121 for Minecraft 1.7.2 loading

[23:45:45] [main/INFO] [FML/]: Java is Java HotSpot 64-Bit Server VM, version 1.8.0_25, running on Windows 7:amd64:6.1, installed at C:\Program Files (x86)\Minecraft\runtime\jre-x64\1.8.0_25

[23:45:45] [main/DEBUG] [FML/]: Java classpath at launch is C:\Users\Owner\AppData\Roaming\.minecraft\libraries\net\minecraftforge\forge\1.7.2-10.12.2.1121\forge-1.7.2-10.12.2.1121.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\net\minecraft\launchwrapper\1.9\launchwrapper-1.9.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\ow2\asm\asm-all\4.1\asm-all-4.1.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\scala-lang\scala-library\2.10.2\scala-library-2.10.2.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\scala-lang\scala-compiler\2.10.2\scala-compiler-2.10.2.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\java3d\vecmath\1.3.1\vecmath-1.3.1.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\net\sf\trove4j\trove4j\3.0.3\trove4j-3.0.3.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\ibm\icu\icu4j-core-mojang\51.2\icu4j-core-mojang-51.2.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\net\sf\jopt-simple\jopt-simple\4.5\jopt-simple-4.5.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\lzma\lzma\0.0.1\lzma-0.0.1.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\paulscode\codecjorbis\20101023\codecjorbis-20101023.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\paulscode\codecwav\20101023\codecwav-20101023.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\paulscode\libraryjavasound\20101123\libraryjavasound-20101123.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\paulscode\librarylwjglopenal\20100824\librarylwjglopenal-20100824.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\paulscode\soundsystem\20120107\soundsystem-20120107.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\io\netty\netty-all\4.0.10.Final\netty-all-4.0.10.Final.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\google\guava\guava\15.0\guava-15.0.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\apache\commons\commons-lang3\3.1\commons-lang3-3.1.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\commons-io\commons-io\2.4\commons-io-2.4.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\net\java\jinput\jinput\2.0.5\jinput-2.0.5.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\net\java\jutils\jutils\1.0.0\jutils-1.0.0.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\google\code\gson\gson\2.2.4\gson-2.2.4.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\com\mojang\authlib\1.3\authlib-1.3.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\apache\logging\log4j\log4j-api\2.0-beta9\log4j-api-2.0-beta9.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\apache\logging\log4j\log4j-core\2.0-beta9\log4j-core-2.0-beta9.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl\2.9.0\lwjgl-2.9.0.jar;C:\Users\Owner\AppData\Roaming\.minecraft\libraries\org\lwjgl\lwjgl\lwjgl_util\2.9.0\lwjgl_util-2.9.0.jar;C:\Users\Owner\AppData\Roaming\.minecraft\versions\1.7.2-Forge10.12.2.1121\1.7.2-Forge10.12.2.1121.jar

[23:45:45] [main/DEBUG] [FML/]: Java library path at launch is C:\Users\Owner\AppData\Roaming\.minecraft\versions\1.7.2-Forge10.12.2.1121\1.7.2-Forge10.12.2.1121-natives-3127370512733404

[23:45:45] [main/DEBUG] [FML/]: Enabling runtime deobfuscation

[23:45:45] [main/DEBUG] [FML/]: Instantiating coremod class FMLCorePlugin

[23:45:45] [main/DEBUG] [FML/]: Added access transformer class cpw.mods.fml.common.asm.transformers.AccessTransformer to enqueued access transformers

[23:45:45] [main/DEBUG] [FML/]: Enqueued coremod FMLCorePlugin

[23:45:45] [main/DEBUG] [FML/]: Instantiating coremod class FMLForgePlugin

[23:45:45] [main/DEBUG] [FML/]: Added access transformer class net.minecraftforge.transformers.ForgeAccessTransformer to enqueued access transformers

[23:45:45] [main/DEBUG] [FML/]: Enqueued coremod FMLForgePlugin

[23:45:45] [main/DEBUG] [FML/]: All fundamental core mods are successfully located

[23:45:45] [main/DEBUG] [FML/]: Discovering coremods

[23:45:45] [main/INFO] [LaunchWrapper/]: Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

[23:45:45] [main/INFO] [LaunchWrapper/]: Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker

[23:45:45] [main/INFO] [LaunchWrapper/]: Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

[23:45:45] [main/ERROR] [LaunchWrapper/]: Unable to launch

java.util.ConcurrentModificationException

at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_25]

at java.util.ArrayList$Itr.remove(ArrayList.java:865) ~[?:1.8.0_25]

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:?]

Update Forge.

There is no reson to stay on 1.7.2, MOST .2 mods will work fine on .10

Beyond that just freakin update, or read the eaq it answers this exact issue in like 3 different ways.