Kirk,
I don't think there's any sense in mailing you files to help you reproduce it; for me it happens to ALL (non graphics) files, even if I simply create one on the command-line. E.g., even a file created using touch ~/Desktop/aaaTTT shows up as aaattt in the contact sheet.
I still reckon this is an issue with Tiger vs. Leopard. Have you tried to reproduce this on a Leopard 10.5.7 system already? Oh, and what file system are you running on, perhaps this has anything to do with it? Mine are all Mac OS Extended (Journaled), non case sensitive (the problem exists on FAT32 volumes as well though, I just tested this on an external disk).
Thanks