I believe you can do an archive and install, that should sort out the problem. However, if it is an update related issue, you want to be sure NOT to update until at least 10.5 comes out, or after you are able to move your media.

I had a problem with my MBP not going to sleep and it turned out the issue was a buggy install of MS office. I didn't have to reformat, just archive and install a fresh version of OS X.

Basically you reboot the machine with the OS X disk that came with it, then follow the instructions. Just make sure you DO NOT choose format, you just want to archive the existing OS and install a fresh one with it. You'll have two OS's on the drive, eating up a little more space, but the new one should work like before. You'll be able to access all of the old files, but will have the functionality of the old OS as well.

I hope that works for you, if not, I'm stumped.

Cheers