Solution:Set the date and time.
Details:So I had an old Powerbook G4 lying around that someone had given me. I hadn't used it in a while, and I turned it on, plugged a USB drive in, and tried to copy some files. I got an error message saying there wasn't enough disk space. Strange, as there was plenty of space, on the hard drive and the USB drive. I ctrl-clicked on the hard drive, clicked get info, and the space wasn't even reporting. Even more strange.
Well... turns out it was the fault of my own laziness. When I first booted the laptop, it said that the date had been reset, probably because the CMOS battery was dead. The error said that I'd probably have problems until I fixed the date, but hey, I just wanted to copy some files off, nothing serious.
Well, while I was putzing around, I decided to go ahead and set the date and time. Lo and behold, my problem went away. If I hadn't been so lazy and paid more attention to the error message I wouldn't have had the problem in the first place. Lesson learned? We'll see... :)