Yes - I'd recommend DISCONNECTING the drive after using it, as indicated in my first post.
Your "System Error 55" is probably a result of NOT disconnecting, and trying to re-connect, (attempting to re-connect to an existing network drive)
I'd suggest checking if the path exists (use the perl "-e" operator). Run the "NET USE" command only if the path does not already exist.
“PHP is a minor evil perpetrated and created by incompetent amateurs, whereas Perl is a great and insidious evil perpetrated by skilled but perverted professionals.”
― Jon Ribbens