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.

Adobe’s fix for these MultiMaster related crashes to either deselect “Font Preview Size” in Photoshop’s Preferences->Type, or remove the conflicting fonts.  They have posted a FontTest script here, that claims to scan for fonts that can cause these crashing issues:
Some people have found that giving a conflicting MultiMaster font wide open permissions will prevent it from crashing Photoshop CS5 (and old school trick Techcare has been using for years), and rumor is Adobe is working on a fix.

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.

As with previous versions of AppleJack, simply run the installer and it will update previous versions if found.