Can't get CS3 to print to my HP 4550 printer

This ones really frustrating!!!
I have 3 Mac machines all running Leopard, 2 Mac Book pros and a mac mini.
No mater what I do I can't get them to print to an HP 4550 color Laser Printer.
Everytime I send something from Photoshop CS3 I get the same result, either it doesn't print at all and I get a message in the print queue that the printer is offline or it sends something to the printer but all I get is garbled rubbish on the page.
I have tried everything I can think of from drivers to setting the printer up as a shared printer on a PC and then sending print jobs via the PC.
The PC works fine but as soon as I send something from the Macs to the printer I get the same rubbish result.
Just to mention, the printer is oldish and doen't have a USB connection so I'm using a cable converter to change from the parallel connection it does have, to a USB port. This seems to work fine as I have tested the cable on PCs and it works.
When I originally set up the printer with my macmini it did work but suddenly its stopped so I know it must be possible.

Any thoughts would be appreciated