Adobe has disclosed in a recent TechNote that Photoshop CS5 can crash when doing a variety of tasks if you have certain MultiMaster fonts installed/activated. Unexpected quits can occur when clicking the mouse, using type, pressing tab, launching Photoshop, or just working on a file.
After a long 11 month wait, AppleJack is now Snow Leopard compatible! This indispensible troubleshooting tool was updated to version 1.6 on 7/12/10, now supporting Mac OS X 10.4-10.6. http://applejack.sourceforge.net
As with previous versions of AppleJack, simply run the installer and it will update previous versions if found.