Please do a search in the forum Mac users have started threads on the problems already
I found the solution on this thread: Full Screen Mode with Menu Bar issue with multiple monitors
Turning off »Use Graphics Processor« in the Performance Preferences (Photoshop > Preferences > Performance > Graphic Processor Settings) and restarting Photoshop
this worked for me.
But turning off the use of your GRO also trune off some Photoshop features like 3d, The rotate tool, liquify etc.
Oh yes, thats not good. Have you figured out a workaround? Anyone?