Can you tell us more about your configuration? What is the make and model of the printer and how is it attached? Is it a network printer or is it a local printer attached to one of your computers? How many computers are affected and what operating systems are in use? Is OneCare on all of the computers?
If you open OneCare on any computer than can't print to the printer (and, specifically on the computer that the printer is attached to, if it is a local printer) and click on Change Settings, and then disable the OneCare firewall temporarily, can you then print?
And, finally, are you trying to use the Printer Sharing feature in OneCare where it should offer to Share the printer to all computers in your OneCare Circle?
-steve