here's a link to a PS troubleshooing page
http://www.gballard.net/psd/troubleshootpurgepsd.html
you could try this...
Trashing Preferences:
If you're trying to rule out Photoshop corruption or reset Default settings, FIRST try trashing:
HardDrive> User> Library> Preferences> Adobe Photoshop 7.0 Settings folder.
HardDrive> User> Library> Preferences> com.adobe.Photoshop.plist file.
There are several other Photoshop preferences there you may trash.
Relaunch Photoshop.
If the problem has not cleared, Mac OS 10, Trash the following (and reinstall Photoshop):
HardDrive> Applications> Adobe Photoshop 7/CS folder.
HardDrive> User> Library> Preferences> Adobe Photoshop 7.0 Settings folder.
HardDrive> User> Library> Preferences> com.adobe.Photoshop.plist file.
Reinstall Photoshop.
Run all Photoshop Updaters adobe.com.