Hi Mark,
I've seen issues with HP Printers for years now, seems they don't clean up behind themselves very nicely.
Their DMExtra collection where all of the "custom" options are saved in DEVMODE returned an invalid StructSize which case CR to throw an exception, there were others but I don't recall the details now...
Crystal the PC's default printer if no printer is selected or the printer the report was designed against cannot be found. Possibly it's simply trying to find the printer.
Have they let it go to see if it ever returns control back to your app?
Do they actually have the printer installed locally?
Don