Try adding in some testing. Such as:

 Code:
use list
"Userid = " @USERID ?
"Domain = " @DOMAIN ?
$MAP1 = "\\fs\fsc$\HomeDir\" + @USERID + "." + @DOMAIN
"Going to map: $MAP1" ?
use m: /delete
IF @ERROR <> 0
   "There was an error deleting m:" ?
   @SERROR
EndIf
use m: $MAP1
IF @ERROR = 0
   "The drive was mapped" ?
Else
   "There was an error mapping the drive. " + @SERROR ?
EndIf


Or something like that.