I think you eluded to this being run as a GPO startup script. If so you have two options to "fix" the issues with Windows 7 (and Vista).

The easy fix is deploy a reg hack. Unfortunately it is not supported by Microsoft and lowers the security of the pc.

The second option, while not difficult, is to map the drives in the context of the user.

See if this link provides you with the info you need: http://www.kixtart.org/forums/ubbthreads.php?ubb=showflat&Number=198514#Post198514