What user is the ColdFusion service set to run under. If it
default "localhost" user, this user has no permissions to
systems via either a mapped drive nor a UNC path.
You have to either give the localhost user on the CF system
to the remote systems or, a better pratice, create a specific
the ColdFusion service with the required permissions what
this CF server
needs to do.
If you plan to use a mapped drive, remember that the given
needs to have the mapping, not just the people who log into