With my 811, I have an OTA outdoor antenna for locals out of Milwaukee. All the way across top of image is a white line that kind of flickers up and down slightly. It only appears to happen on NBC digital channel, which has black bars on all four sides of image. If image could be moved up about 1/2" it wouldn't be seen. Anybody have any ideas, the line is driving me crazy. Could it possibly be the TV network's problem? Thanks.