Rwd, That was my reco on 4-17-05. Unplugging the unit for a few minutes then plugging it back in. I've never had a problem with my SDS yet, but that's worked on computers, dvd players, tv's and cd players. As more computer software gets into our audio hardware, sometimes all it takes to get something working again is to unplug it and reboot the system.
It's a very inexpensive fix, and the first one I try. :-)