I'm trying to develop with NEI installed into the eclipse environment, but am not successfully getting it working. I've followed his instructions on the MCForum topic, added the _at.cfg's to the right places and all. But I am still getting this error:

 

2013-06-06 08:21:39 [iNFO] [sTDOUT] Adding Accesstransformer map: codechickencore_at.cfg
2013-06-06 08:23:06 [iNFO] [sTDERR] Exception in thread "main" java.lang.RuntimeException: java.lang.RuntimeException: java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:192)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at cpw.mods.fml.relauncher.FMLRelauncher.relaunchClient(FMLRelauncher.java:104)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at cpw.mods.fml.relauncher.FMLRelauncher.handleClientRelaunch(FMLRelauncher.java:38)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at net.minecraft.client.Minecraft.main(Minecraft.java:2237)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at Start.main(Start.java:29)
2013-06-06 08:23:06 [iNFO] [sTDERR] Caused by: java.lang.RuntimeException: java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:306)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at cpw.mods.fml.relauncher.FMLRelauncher.setupHome(FMLRelauncher.java:172)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	... 4 more
2013-06-06 08:23:06 [iNFO] [sTDERR] Caused by: java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at codechicken.core.asm.CodeChickenAccessTransformer.readMapFile(CodeChickenAccessTransformer.java:44)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at codechicken.core.asm.CodeChickenAccessTransformer.addTransformerMap(CodeChickenAccessTransformer.java:30)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at codechicken.core.asm.CodeChickenCorePlugin.call(CodeChickenCorePlugin.java:123)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at codechicken.core.asm.CodeChickenCorePlugin.call(CodeChickenCorePlugin.java:1)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at cpw.mods.fml.relauncher.RelaunchLibraryManager.handleLaunch(RelaunchLibraryManager.java:302)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	... 5 more
2013-06-06 08:23:06 [iNFO] [sTDERR] Caused by: java.lang.reflect.InvocationTargetException
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at java.lang.reflect.Method.invoke(Method.java:597)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at codechicken.core.asm.CodeChickenAccessTransformer.readMapFile(CodeChickenAccessTransformer.java:40)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	... 9 more
2013-06-06 08:23:06 [iNFO] [sTDERR] Caused by: java.lang.IllegalArgumentException: resource codechickencore_at.cfg not found.
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at com.google.common.base.Preconditions.checkArgument(Preconditions.java:119)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at com.google.common.io.Resources.getResource(Resources.java:191)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	at cpw.mods.fml.common.asm.transformers.AccessTransformer.readMapFile(AccessTransformer.java:107)
2013-06-06 08:23:06 [iNFO] [sTDERR] 	... 14 more

 

I googled it, others have had this problem, but no solution was ever posted. Any help would be great.

Try to look for a NEI API in the official forum post. You dont need to decompile NEI for that.