Windows 7: HP designjet 450 networking problems

Hello,

I'm not sure if this should be in hardware or networking but I think it is a printer problem so I will try here.

My problem is that I have a HP designjet 450 CAD plotter in the office which I need to be able to print to from two computers. Both computers are running windows 7 64bit and I have shared the printer on the network so that I can see it on the other PC. We have also got a homegroup running on these PC's for file access. Now, with the HP plotter successfully installed on the shared computer I can print a test page only. No other documents seem to send to the printer as they dont show up in the queue at all. I have researched online for this problem but have been unable to find a fix, can anybody help?

Thanks

Michael