Quite possibly something I've messed up myself. When I'm editing a Ruby file and I hit command-R to run the file, I get a pop up window called 'Run' indicating problems. I can't even copy the text from that window (it doesn't seem to make it to the clipboard) though the ultimate problem appears to be that something is trying to invoke '+' on nil. I've a attached a screenshot of the full error report.
Is this a simple, obvious problems? (Well, I mean to people other than me :-) ).
Thanks, Ken