I'm not sure what the problem is ... I don't really know how to diagnose it either. When I try to run Photo Booth the icon bounces once and the program never runs. The camera is functional, I can access it using Quicktime (File -> New Movie Record).
The same thing happens with Software Update ... I go to
-> Software Update and the icon shows up in the Dock and disappears immediately. 
EDIT: I installed Tiger over Leopard using the "backup this system and do a full install" method, but some applications seem to still exist in /Applications. I should probably backup, format, and do a completely fresh install. I need to go buy an external harddrive first ...
The same thing happens with Software Update ... I go to

EDIT: I installed Tiger over Leopard using the "backup this system and do a full install" method, but some applications seem to still exist in /Applications. I should probably backup, format, and do a completely fresh install. I need to go buy an external harddrive first ...