Strangest error on functioning code blocks

Hi all,

Now and then I get the strangest errors on code. It indicates one or more whole function(s) is/are erroneous. I've seen it happen on my own code, on the Feathers UI code and can not make anything of the error Flash Builder produces (see attached image). The error goes away after some 'fiddling' with the code (nonsense modifications and saving again) or sometimes a "clean project" occasionally it's stubborn enough to make me restart the whole thing (sigh).

Can anyone make anything of this error?

Using:

FB 4.7

OSX 10.9.4

Thanks in advance,

Manno