Don't use a Mac but from previous post here is one suggested solution.
What happens if You hit Your Application Frame’s green button?
I don’t use Application Frame myself, but if all else fails I would consider trashing prefs (holding command-alt-shift on starting Photoshop) after making sure all personalized items (Brushes, Actions, Keyboard Shortcuts, etc.) are saved and the Preferences settings are noted (for recreation after trashing).
Curt, thanks for your reply. I tried it but it didn't help.
Now, I tried the green button and that fixed it! So simple....