Originally Posted by rschulz
if there is anything else i can do to help troubleshooting this without endangering another piece of hardware, please let me know. i will happily sent the apparently broken card to Nvidia for inspection.
My card was not in fact broken, despite what NVidia say. After installing the 64-bit driver the card refused to show any output when using a DVI cable between the card and the display(s). I switched to using a VGA analog cable with a DVI-VGA converter at the card end (my display has VGA and DVI inputs) and it just worked again.
I still believe there was/is something screwy in the 64-bit version of the driver that put the card into an odd mode so that it would not output via DVI. As a result of the lack of response here and from NVidia directly I have decided to no longer buy NVidia video cards.