Ok, I give up: What is with the tension between "FYR" Macedonia and Greece Proper?

Just as an interesting addendum to this thread: at the Ireland-Macedonia Euro 2012 qualifier last night, the Macedonian fans were holding a banner that said “One Name - One Nation”.

Updating this thread:

If only it was that! At least it would made a shred of sense. But no. Since the collapse of Yugoslavia, Greeks have been a massive pain about this issue, simply because they can’t stand that a neighboring state claims the name of the country of origin of their great national hero and Macedonian historical heritage. That’s nationalism, but at an even vastly lower level than you guessed.

OK, once again, posted first and realized later that everything has been covered years ago. Sorry.