I use PDFCreator, which is a neat and free piece of software. However, it has problems properly printing under some conditions. The easy fix is to open Printers, left click PDFCreator, pick "Printer properties", go "Ports", "Configure Ports", tick "Run as user".
Under XP, this fixed it all, with 7 I get the following error: "An error occurred during port configuration. Operation could not be completed (error 0x00000001)."
How can I bypass it?