Screen print separations

We are currently using a Mac Mini & Illustrator CS5 to print our separations. We print to a 2010 HP 5200. We are able to change our halftone dot manually to 45 lpi with no problems.

Our issue is this: We have started using Creative Suite on a PC and when we try to print the same separations it will not print the halftone dot at 45 lpi, even though we can manually change it.

Can anyone help with this issue. Is this a older printer / creative suite issue?

Thanks