Yes! That's the magic solution! Thank you for directing me to that thread, which I hadn't seen before.
Everything's good now.
I do in fact run Windows (Vista), but it is on an NTFS volume. I set up a large FAT32 partition for my games and for transferring files from OS X to Vista. I didn't pay attention to the .Trashes in there, but that was the problem. There was a file that appeared to be something like ¬ or ￢. Strange, yes, however a simple permanent delete of the 501 folder seems to do it. I ran a Chkdsk /F /X just in case, which returned no errors.
Thanks so much everyone who helped me through this. I hope others will the same problem will have an easier time finding the solution now.
I don't know if Apple support would be able to help if they even knew about this issue. Anyway. Case solved.
If you have a windows partition, usually formatted as FAT 32, there is a problem with the .Trashes folder on that partition. The folder is hidden while viewing the files in the Mac Finder, but it can be seen when booted into windows.
I repaired the problem by booting into windows using Parallels and running the Check Disk Utility for windows hard drives. (Open My Computer, right click on the C drive and click properties. Click on the tools tab, then click repair hard drive. Make sure there is a check in the box that says "repair errors". Then you will be prompted to reboot. Check Disk will run on reboot)
Check Disk found the error in the .Trashes/501 folder and repaired it. Now my Trash in OS X does not have the strange characters when I empty it.
I haven't tried it, but I would assume that if I just booted into windows, (through bootcamp or Parallels, or VMWare Fusion) and deleted the .Trashes folder on the C drive, that would work also. If you have an external drive formatted in FAT 32, you can plug it into a windows machine and you should be able to do the same thing.