Using Photoshop 12.1 (12.1x20110328 [20110328.r.145 2011/03/28:10:30:00 cutoff; r branch]) x64
on Mac OS 10.6.8
Something very wierd that happens with any image. Photoshop opens file correctly, I can perform any single command once (example rotate by 180 degrees or resize image) and it is done correctly. After that command cannot switch between stacked panels. If I have floating panels, I can still use them and they work ok, but I cannot move them nor resize them. Furthermore when this happens (it does happen with nearly every command, but not all) if I close the image no matter if saving it or not, whatever image I open next, I cannot see it, but it is effectively open, because I can perform some image-wide operations, save the image and they are applied. If I quit Photoshop and open it again, everything works fine again till next command.
Tried starting Photoshop as 32-bit, but no difference. I have tried resetting the Plugins and Preferences but that didn't help. It seems that booting Mac in Safe Mode solves the problem, but of course it is not a definitive solution.