Please read this:
http://forums.adobe.com/thread/375816?tstart=0
And be aware that this Forum is announced to be shut down today, check out the
http://forums.adobe.com/community/photoshop/general
Boilerplate-text:
Are Photoshop and OS fully updated?
As with all unexplainable Photoshop-problems you might try trashing the prefs (after making sure all customized presets like Actions, Patterns, Brushes etc. have been saved and making a note of the Preferences you’ve changed) by keeping command-alt-shift pressed on starting the program or starting from a new user-account.
System Maintenance (repairing permissions, purging PRAM, running cron-scripts, cleaning caches, etc.) might also be beneficial, Onyx has been recommended for such tasks.
http://www.apple.com/downloads/macosx/system_disk_utilities/onyx.html
Weeding out bad fonts never seems to be a bad idea, either. (Validate your fonts in Font Book and remove the bad ones.)
If 3rd party plug-ins are installed try disabling them to verify if one of those may be responsible for the problem.
