Network printer erratic

We have 2 workstations running XP Professional.
We installed our network printer indentically on both (TCP/IP) ie created a
port etc. running on a Chase Research (Perle) print server (following their
instructions) on both machines but now one machine continues to work
normally whereas the other spools the job but then hangs - throwing out
various messages including sometimes stopping the print spool service or
else killing communication with the printer server which then needs
rebooting (ie won't respond to a ping from the workstation).
The printer is a Sharp AJ-6110 which we use only for colour printing and
photocopying (not scanning).
The driver isn't digitally signed although Sharp say it is designed for XP
We have a second HP printer on another print server (DLink) - that continues
to work perfectly on both workstations suggesting that TCP/IP is continuing
to operate properly so we are really confused...

Stuck!

Do we revert to win98SE?
Is that the only answer?
Should we uninstall and reinstall the TCP/IP protocol?
Where else should we look for a clue?
Thanks
Jonathan