Hi William,
Your approach with 'printing' to screen sounds interesting as it might be an option to verify printouts in the .pdf format and the like. Problems with verification of .pdf files were discussed here quite often but the general solution so far was to convert original document into text format (losing formatting and the most of layout) and then compare just a textual part.
Are you using some system drivers (never heard about them) that print directly to (some window on the) desktop or some third-party software like SnagIt that installs its own printer driver that can be used to print to the SnagIt application?
Anyway, I agree that your assumption about the root of the problems most probably is the right one.