Whoops, I over edited... this is what it was supposed to say...
I'm in the same position. Every kind of installer program or updater, apple or 3rd party, stops responding as soon as I hit install. I can pick the volume agree to the contract, etc. I have repaired permissions, repaired the disk, created a new user, changed passwords, checked for the temp file (it's there) all for naught. I don't get any messages either, just that inssuferable beachball.
Also, my powerbook G4 has just awoken from a several month slumber. I believe the firmware was corrupted and it kept sending me to that white screen with command prompt, regardless of what keys I pushed with the install CD in the drive. I forget what that white screen is called... I tried everything in the book for that one too, mac-boot, etc., but I eventually gave up. I was going to take it into the mac store tomorrow and turned it on just to see and it booted up just fine but now I can't install the updates from the past few months...