I'm using my IDEA license normally on Windows, but sometimes on OS X, too.
When I launch IDEA (#9902) on OS X, a "License Collision Detected" dialog
pops up on the Windows machine (#9902, too). Even after I have switched off
the Mac, pressing Yes to re-activate IDEA on Windows, the dialog pops up
again and again. I need to click No and restart IDEA. Very annoying.