Running a simple directory listing using the /tc switch to show create time showed that the create time of the directory was wonky.
r:\> dir /tc
Directory of R:\
The parameter is incorrect
07/12/2001 11:18AM <DIR> Public
After writing a utility to change the create time to a valid value, everything worked as it should.
We believe this drive was actually created under NT4 and has been migrated ever since, which could account for the error. Very odd, though.