urgent help needed

OK here's one that's got me stumped. Windows NT 4.0
Server, Service Pack 6, all up to date on security
patches. It acts as a print server for about 15 or so
printers most of them HP Jet Direct Printers. However
their are two Xerox Phaser Printers on it as well. These
printers are connected via LPR ports. Here is the part
that defies logic. From any client PC you can ping the IP
addresses of the LPR printers, from the server you can
ping the addresses of all client machines and Jet Direct
printers, however from the server you CAN NOT ping the IP
addresses of the LPR Printers. The TCP/IP settings on the
LPR printers are 100% These printers were working fine on
the server in question, but for some mysterious reason
they stopped working... Why can't I ping these printers?
Why can everything but the server ping these printers? I
know this is step one in fixing this problem HELP!