10.1 Upgrade/QT Player Won't launch


Help, please. I'm now at a loss. The only other step I can think of is to reinstall.
Here's the problem. When I launch Quicktime Player, it crashes instantly every time. The finder plays movies and audio fine. No problem playing off the web either. Just the player app won't open.
Here's the hardware. It's running on an iMac 400 DV SE with 384MB. It's stock other than the RAM upgrade.
What else I have. I have a G4 450 that I also upgraded. QTP works fine.
Here's what I've tried. First I put the original 10.0 QT Player 5 back on. It didn't work either, so I burned it. Then I copied the player from the G4, which still didn't work. Then I copied the prefs from the G4 over - nope. Then I burned all the QT prefs - not. Then I replaced the QT folder in Library from the G4 - nope. Then I also replaced the QuickTime and QuickTimeJava folders in System/Library from the G4. Still a no go. I don't know of anything else that I can replace.
Anyone have any ideas? Thanks in advance.
I'm on an iMac Rev A. upgraded to 466mhz, 60 gig HD, and 192MB of RAM. I have the same problem without a possible fix in sight (other than a re-install) which started when i chose "Save movies in disk cache" in the QT Preference Pane. The player only functions under root user and i have to use Ptah demo to play movies under other users.