I've replicated this issue on a few PCs all running Windows 8.1, so I'm not sure if this is a problem for Win 8 users too.

When we set the printer properties to require printer credentials (a print code set on the printer) to be entered before printing, the prompt sits in the background, minimized to the taskbar instead of popping up in the foreground.

So the user thinks the printing has failed, when it is waiting for the credentials silently in the background.

Anyone have any ideas on how to fix this?