This narrows it down a bit, thanks. I try repeating these
steps with my system tonight. My only guess is that
somehow the date/time routines are seeing this as an
invalid date after you change it, and so aren't setting
the date/time properly. I'll check this. Keep in mind
that the FileModifyDate isn't stored in the file, but
is part of the filesystem. So the file itself is not changed
when you set FileModifyDate.