afaik, it's not been reported here,
or at least I haven't personally seen it...
so how are we supposed to know about it?
Too late now!
5.0 Final is already Final
Sticky: Post ALL Winamp 5 OFFICIAL Plugin Bugs in HERE
Follow the guidelines outlined in the first post
ps. I've got no way of trying to reproduce this, because I'm only using single monitor setup, but someone else on the team does/will.