I have had two USB DACs in house for testing/troubleshooting a third sound card.
I could not get this output mode to playback audio at 16/44 for either USB Dac; one was an M-Audio Fast Track Pro, and my current one is a Peachtree Nova which uses, as far as I know, off the shelf Cmedia, TI/BB PCM270x/PCM290x.
I tried various settings but playback always fails. I can email some logs if that will help. I don't plan on using the Nova DAC via usb but maybe this bug is native to Windows 7 (x64)?
DC