HP4V & Incomplete Plots

We've recently started having problems plotting drawings to our HP4V Laserjet printer. The problem only seems to appear on specific drawings at the moment, but we want to rectify it before it spreads to everything else.

When plotting some drawings to the HP4V not all of the line work appears on the plot. The 'print preview' shows the entire drawing, but when the drawing is plotted out, parts of it are missing. When I say parts missing, one half of a line will plot, then the other half wont. Plus variations on this issue.

I've tried all the standard methods of fixing this problem, exploding objects, changing layers, reloading plotter drivers, etc, but nothing seems to fix it.
The other strange thing is that the drawings print fine to our OCE Plan Plotter, which would suggest that nothing is wrong with the drawings themselves.

If anyone else has experienced this problem I'd be interested to hear how you solved it.
We're currently running Win2K on a Win2K network with AutoCAD 2004.

Thanks in advance
Mike