"NET USE L: \machine_name\drive_letter:\folder_name"
That's you problem - the concept of "drive letter:" doesn't exist on a remote machine, you have to use the share name, so the format becomes:
NET USE L: \machine\share\folder
Try this at the DOS prompt to verify that you can connect before putting it in the logon script. It has nothing to do with the e-smith at this point, it's purely a windoze thing.