File causes loss of drive mapping

Had a 5.1 server lose NDS during hardware upgrade. Recreated NDS and
copied data over to new server. Now, whenever a user accesses a certain
directory/file they lose their drive mapping and have to reboot.

Trying to find a way to delete the file without downing the server(mission
critical apps). We suspect a virus, but when anti-virus scans file, the
workstation locks, drops the mapping and we have to reboot.

Any thoughts?

Thanks