I suspect it is something to do with the sound.
Display Spoiler
java.lang.RuntimeException: AdvancedSoundManager: Can't find SoundSystem
at ic2.AudioManager.getSoundSystem(AudioManager.java:156)
at ic2.AudioManager.playOnce(AudioManager.java:114)
at ic2.ItemToolWrench.onItemUseFirst(ItemToolWrench.java:66)
at ob.a(PlayerController.java:105)
at net.minecraft.client.Minecraft.a(SourceFile:1130)
at net.minecraft.client.Minecraft.k(SourceFile:1337)
at net.minecraft.client.Minecraft.run(SourceFile:754)
at java.lang.Thread.run(Unknown Source)