My McAfee firewall stops my Dell 926 wireless printer working

What happens is this: it prints when I first switch the computer on (presumably before McAfee has loaded) anything that is in the printer queue, then once McAfee is running it gives a "Printer interface has stopped working" error.

McAfee say I have to add the printer's port number to my permitted system services in the firewall - but what is the printer port number for a wireless printer, do you know?

Thanks!