Hrothgar, Calmon means the CD key from inside the manual. Clean install, re-do the key (triple checked) to make sure it is correct.
System specs and OS would be useful.
Otherwise, make sure to post here if you resolve it
But if not, let Shrapnel know. There is another thread with similar problems.
Shrapnel Support:
http://www.gamersfront.com/xcart/support_ticket.php