Yes, I just tried this.  Moreover, an error occurs when trying to
write the output of BACKUP DEVCONFIG or BACKUP VOLHISTORY
as well.  Slightly different messages, etc., but the same basic
problem.

My ADSM server is running on NT; using the "System Account"
as its logon id in the service profile.
Perhaps that id doesn't have access to open a file
on the mapped drive? (the actual drive is on another NT
system, on the same LAN, in the same NT domain).

John Sorensen
SSSI