XP/DELL/HP printer issue

be grateful if anyone can suggest a fix for this printer problem please!.

DELL XPS 210 core2duo E6600 proc. 2.44 Ghz (just 1 yr old)
Win XP / SP2 already installed + service updates
Printers: HP 350C DesignJet Plotter & HP DeskJet 1220C printer
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on a regular basis, when sending a print to either machine (especially the
plotter), it sends the print, but fails to print!, the only resolution is to
close down the whole set-up and restart and immediately on bootup the prints
start once this is complete!. Drivers are as updated as HP have on support.
(no error messages are displayed - just fails to print).
rather annoying process to have to keep doing.

any suggestions please?.
thank you!.