Thanks for the tips Ron, the.xlb file was the cuplrit. It took a
couple tries to get rid of it, or maybe it was getting corrupted/
bloated again immediately.

Still don't know specifically what caused it, although I believe the
copying and pasting between files open on the email server and files
on the user's local disk has something to do with it. If anyone has
any answers or ideas, please share.

FYI if anyone is interested - it wasn't just this file that was having
the issue, it was Excel itself. I should have checked that before
posting. This explains why the new file with just values and formats
pasted in had the same issue.(duh) Don't you love it when things go
wrong late on Friday afternoon?

Thanks!
Cliff Edwards