1st – Was the old DC 2000 or 2003? Is the new DC SP1?
2nd – Are the printers IP addressed or furnished by local PCs?
3rd – Have you verified the firewall openings for printing?
If I had to guess, it would probably be the 3rd question that points to the answer. The new server is not providing a service (RDP?) in the same manner as the old one did. If you ran the ‘Security Configuration Wizard’, there was on one of the umpty-ump pages a section on Terminal Services. I would start there.