I'm running FCP 5.1.1 on a G5 Quad, everytime I delete FCP Prefs I loose the ability to use RED and also Continuum. It takes away the button to access the settings. I then find that I have to re-install the update and everythings once again fixed. I use FCP Rescue, does that have anything to do with it?
Just wondered, are we looking at huge speed increases when the Mac Pro versions come out?
Are you doing the shift-lock trick? (Delete the cache, start FCP with lock on, immediatly quit, then start FCP with lock off). There is a known issue with Boris and FCP 5.1.1 where the controls for Boris disappear but are restored by this trick.
I don't know if FCP Rescut could causing trouble- It has definitly saved my bacon in the past.