Whenever I open my Sharing control panel, Systems Preferences crashes. It only happens with Sharing and only on my Wall Street Powerbook. No problem with the G4 tower.
I think I read somewhere about how you can trash the preference files in OS X and let them rebuild but I don't remember the...
During the PB, it seemed the loudest screaming came from people who wanted the exact opposite...
Anyway, I believe the desktop is still a folder so perhaps you could just make it read-only? (This would only apply to the Desktop Folder in your user directory, of course.)