HP LaserJet IIID Error Message

I need to know what ’51 Error’ means on an HP LaserJet IIID and how to fix it.

The printer is on a Windows 2000 print server. The print job goes into the queue and is sent to the print device. The print device begins to process the job, then reports ’51 Error’ and prints a blank sheet of paper with a black streak of ink.

We have already reset the Jet Direct box.