The last couple of days my G4 1.42 Dual running Tiger and FCP 4.5 was just freaking out, getting beachballs everywhere in all apps. This morning it was also not seeing my two Firewire drives either, and Disc Utility couldn't find any drives. So after re-connecting all my cables and re-starting a couple of times, the drives came back and I was able to repair permissions.
To my amazment, all the problems seem to be gone. I was about to do a clean install it was so bad. Can permissions repair really be this powerful?
I'd say No. but others will argue permissions are the most powerful tool at your disposal but the operation may or may not have been related at all to your situation. that is, repairing permissions may have only been coincidental with your system purging a huge and possibly damaged swap file. Were there any longer than normal startups during any of these sessions? That endless gray screen can indicate tremendous disk repair activity.
If you google "repair permissions" you will find hours and hours of fascinatingly incomprehensible discussion including the proposal that it's completely irresponsible of Apple to make such a powerful and seemingly required management tool so completely opaque and non-user friendly.