I have a Denon 1910, GTX-460 and Win7 32. Randomly, after switching the monitor configuration or power cycling the AVR, Windows will drop the GTX as an audio device – it does not show up at all under the Sound Control Panel. I can only fix with a re-boot.
This sounds a little different than your un-plugged issue, but maybe related. It is fairly annoying. No idea on any other solution.
I also have a ton of issues switching the monitor configuration when using the projector/tv driven through the AVR with the GTX-460. I usually have to power cycle the AVR, switch the monitor configuration, then power cycle again to get the change to take.
I just swapped out my GTX-460 to RMA it – one of the DVI ports went bad. My GTX-9800+ has no switching issues at all in the exact same setup. I wonder if this is a driver issue or a the way the design is implemented by different manufactures – the 9800 is a PNY card and the 460 is made by Sparkle.
Anyone else have any feedback on specific 4 series cards and how well they play with AVR switching?