How about your USB drivers? Win 7 does not always detect your USB 3.0 hubs, and this can sometimes cause issues.
You can usually only tell by counting the USB devices in your device manager and comparing them to how many your board should have. For instance, I'll have about 8-10 before installing the correct drivers and 14 after.
Other than that, I would clean out any of the DAC device drivers I could find in Win 7, reboot with the device unplugged, and start over. If that didn't work I might do a registry search and make sure any mention of the device was gone.
And, obviously, see if you can get it working with a different computer.