That wasn't it but I contacted Adobe and this fixed the issue:
-
Re-create the Photoshop CS5 preferences file:
Quit Photoshop CS5.
Rename the Users\[username]\Library\Preferences\Adobe Photoshop CS5 Settings\Adobe Photoshop CS5 Prefs.psp folder to Adobe Photoshop CS5 Prefs.old.
Start Photoshop CS5. Photoshop creates a new Adobe Photoshop CS5 Prefs.psp file.
-