ArcToolbox script will not return values

Discussion created by DrColgate on Sep 6, 2011
Latest reply on Sep 12, 2011 by philmorefield
Okay most of that stuff in here before was redundant so it seems.

New toolbox, new Script.  No changes made to validation.  No input at all.  Just a straight run of the script does not work.

import arcpy
mxd = arcpy.mapping.MapDocument("current")

Hopefully that is a bit easier to answer cos I reckon I must be missing something really, really simple.