For the last couple days I've been having this odd problem with one of my receivers which has gotten progressively worse. I'll have it tuned to a channel and it will seem to be fine and then it will pop up a 771/searching for signal message then often the audio or video feed will change to that of a different channel for a moment or two, then back to the correct one again. After this happens a couple of times, the box reboots itself. This will happen with both tuners. It is an HR21-700. My other receivers (same SWM via same splitter) are not experiencing this. However, I haven't yet had the chance to go outside and check the cable connections. Any ideas of what this could be and what I should start looking at first?