I am having the same problem as this guy.
"I'm on a dual 800MHz G4 w/1GB Ram. I only use this cpu for basic internet and email. Monday I booted it up and it said a new version of Quicktime is available. I don't remember what version it said, but I told the prompt to go ahead and automatically...
Sorry all. The different threads had me confused and I have NEVER done this before.
I think it worked!!!! I can't believe Stuffit caused this problem all along!