im having the same problem with EVERYTHING so i treid downloading scala library , now i get THIS :
Instance started with command:
"java" -Xms512m -Xmx1024m -jar MultiMCLauncher.jar "test" "Offline" "MultiMC: Modded" "854x480" "Mojang"
Loading jars...
Loading URL: file:/C:/Users/Jordan/Downloads/MultiMC/instances/Modded/minecraft/bin/minecraft.jar
Loading URL: file:/C:/Users/Jordan/Downloads/MultiMC/instances/Modded/minecraft/bin/lwjgl.jar
Loading URL: file:/C:/Users/Jordan/Downloads/MultiMC/instances/Modded/minecraft/bin/lwjgl_util.jar
Loading URL: file:/C:/Users/Jordan/Downloads/MultiMC/instances/Modded/minecraft/bin/jinput.jar
Loading natives...
Fixed Minecraft Path: Field was private static java.io.File net.minecraft.client.Minecraft.an
Launching with applet wrapper...
2013-05-12 12:49:43 [iNFO] [ForgeModLoader] Forge Mod Loader version 5.2.6.696 for Minecraft 1.5.2 loading
2013-05-12 12:49:43 [iNFO] [ForgeModLoader] Java is Java HotSpot Client VM, version 1.7.0_21, running on Windows 7:x86:6.1, installed at C:\Program Files (x86)\Java\jre7
2013-05-12 12:49:43 [iNFO] [sTDOUT] Loading Coremod
2013-05-12 12:49:43 [WARNING] [ForgeModLoader] The coremod mab.coremod.commander.CommanderCoreMod does not have a MCVersion annotation, it may cause issues with this version of Minecraft
2013-05-12 12:49:43 [iNFO] [sTDOUT] get Transformer Class
2013-05-12 12:49:43 [iNFO] [sTDOUT] get Transformer Class
2013-05-12 12:49:43 [sEVERE] [ForgeModLoader] A critical problem occured registering the ASM transformer class cpw.mods.fml.common.asm.transformers.DeobfuscationTransformer
java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.transformers.DeobfuscationTransformer
at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:238)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at cpw.mods.fml.relauncher.RelaunchClassLoader.registerTransformer(RelaunchClassLoader.java:122)
at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:278)
at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:172)
at cpw.mods.fml.relauncher.FMLRelauncher.relaunchApplet(FMLRelauncher.java:259)
at cpw.mods.fml.relauncher.FMLRelauncher.appletEntry(FMLRelauncher.java:229)
at net.minecraft.client.MinecraftApplet.init(MinecraftApplet.java:25)
at net.minecraft.Launcher.init(Launcher.java:108)
at MCFrame.start(MCFrame.java:72)
at MultiMCLauncher.main(MultiMCLauncher.java:275)
Caused by: java.lang.AbstractMethodError
at cpw.mods.fml.relauncher.RelaunchClassLoader.runTransformers(RelaunchClassLoader.java:352)
at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:225)
... 11 more
2013-05-12 12:49:45 [iNFO] [sTDERR] Exception in thread "main" java.lang.RuntimeException: java.lang.RuntimeException: java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.FMLSanityChecker
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:192)
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.relaunchApplet(FMLRelauncher.java:259)
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.appletEntry(FMLRelauncher.java:229)
2013-05-12 12:49:45 [iNFO] [sTDERR] at net.minecraft.client.MinecraftApplet.init(MinecraftApplet.java:25)
2013-05-12 12:49:45 [iNFO] [sTDERR] at net.minecraft.Launcher.init(Launcher.java:108)
2013-05-12 12:49:45 [iNFO] [sTDERR] at MCFrame.start(MCFrame.java:72)
2013-05-12 12:49:45 [iNFO] [sTDERR] at MultiMCLauncher.main(MultiMCLauncher.java:275)
2013-05-12 12:49:45 [iNFO] [sTDERR] Caused by: java.lang.RuntimeException: java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.FMLSanityChecker
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:306)
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:172)
2013-05-12 12:49:45 [iNFO] [sTDERR] ... 6 more
2013-05-12 12:49:45 [iNFO] [sTDERR] Caused by: java.lang.ClassNotFoundException: cpw.mods.fml.common.asm.FMLSanityChecker
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:238)
2013-05-12 12:49:45 [iNFO] [sTDERR] at java.lang.ClassLoader.loadClass(Unknown Source)
2013-05-12 12:49:45 [iNFO] [sTDERR] at java.lang.ClassLoader.loadClass(Unknown Source)
2013-05-12 12:49:45 [iNFO] [sTDERR] at java.lang.Class.forName0(Native Method)
2013-05-12 12:49:45 [iNFO] [sTDERR] at java.lang.Class.forName(Unknown Source)
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:295)
2013-05-12 12:49:45 [iNFO] [sTDERR] ... 7 more
2013-05-12 12:49:45 [iNFO] [sTDERR] Caused by: java.lang.AbstractMethodError
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.RelaunchClassLoader.runTransformers(RelaunchClassLoader.java:352)
2013-05-12 12:49:45 [iNFO] [sTDERR] at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:225)
2013-05-12 12:49:45 [iNFO] [sTDERR] ... 12 more
i AM using multiMC but not reason why the scala library thing would work for anything else either