Powerbook g4 not fully booting to login screen FireWire problems
From what you're seeing I'd guess that the startup drive on your Mac has some sort of file system or directory problem.

If this were my computer, I'd reformat the hard drive and (assuming that went without a hitch) restore from my backup.

If a backup wasn't available, I'd run DiskWarrior (be certain it's a version compatible with the OS on the "borked" drive.) If that failed, I'd try the repair disk function in Disk Utility as a last resort.

Note that it's quite possibile that Disk Utility will repair this disk. Given that Disk Utility is free, one might wonder why I'd opt for the utility that costs money. My reasoning is that DiskWarrior is non-destructive and allows you to preview the "repaired" drive before committing to changes. If you absolutely can't or won't use DiskWarrior, at least use Disk Utilities "verify" mode before attempting the repair.

Unix Gurus might advocate using fsck instead of Disk Utility but I prefer the GUI approach. 

I would also advocate casting a suspicious eye on any disk that you've had to use drastic methods to recover. Given the age of the computer in question, and assuming an original disk drive, my tendency would be to immediately transfer recovered information to a new disk and install that into the computer. In the old days I might put the old disk to work as a "shuttle" drive but in this era of keychain jump drives and DropBox I'd just strip it for bits or send it to the ewaste recycler.