Couple of threads in the Adobe Photoshop forums about this. Seems to be due to a corrupted preference file. I forget the key sequence that you hold down when starting PS to clear the preference file (CTL-CMD-SOMETHING obviously, a quick search ought to get it).
The problem seems to come back and Adobe stated they were working on it.
|Christine by JP Zanotti|
from Car wreck
|Fangorn Forest by cand1d|
|Yosemite Falls with Moonbow by Jonathan Shapiro|
from Best Landscape of the Week 4