Just ran across a computer that was giving the above message when trying to
install one particular HP printer model (any 4600 - no problem with some
other models that were tried). The same 4600 printer installed fine on
other computers. Anyway, it turns out that there was an HP tool installed
on the workstation for a deskjet 5600 (USB) printer that was causing the
problem. After killing the HP app (was in the system tray) the iprint
printer installed fine.

I figured this info might be helpfull to others as I've seen questions about
overlapped io in this newsgroup in the past.