NT4 Network Printing

We have two LPR printers on our NT network. One is a Mita copier and the other is on an HP Print Direct print server. I have set them both up with Microsoft TCP/IP printing on our server. Occasionally, when I print from the server the job goes into the print queue and then disappears without actually appearing at the printer. I don’t get any error messages and the job does not hang in the queue. This results in unreliable printing from any client trying to print through those server shares. Hasanyone seen this before?