Internal compiler error after upgrading to Unity 4...

Internal compiler error. See the console log for more information. output was:BCE0011: An error occurred during the execution of the step ‘Boo.Lang.Compiler.Steps.EmitAssembly’: ‘Empty name is not legal
Parameter name: fullname’.

What does this mean, it was working fine in Unity before I upgraded to 4.

Check for empty JS files. I checked, still got an error, checked through every directory,so rechecked and found an empty one just laughing at me.