"No Printer Drivers" error

Hi all...

We have what seems to be a randomly occurring error...
a bit of background - we have a room with 60+ PCs
running XP, printing to a DOS based queue system, split
to two servers and HP Laserjet 5Ms. Occasionally when
users go to print they get an error which states "
Printer not connected or Drivers no installed"
Sometimes, on the second attemp at printing, the error
goes away, and sometimes it needs the rebooting of both
of the servers, and the PC in qustion.

Anyone have any ideas what cold be up? Could it be
network problems? or is there anything else?
Thanks in advance,
Ewan