android compile problem... what does a small 'x' mean displayed on a source directory?

I have an android project that just doesn't want to compile.  There is a small 'x' on the icon of gen directory.  If someone knows what that means, it might help me figure out the problem.  

I usually can resolve wierd compile problems in android by deleting the out directory and the gen directories, but in this case I can't figure it out.

See attached screen shot.