We are experiencing a white/light gray screen when changing channels. the delay is the longest when we switch the DVR on (wake it up), could last 20-30 seconds. We try to move the channel up/down, sometimes it helps but in most cases it doesn't. Later, after the DVR 'established' itself, there is still a delay although much shorter one. Any idea what this could be? We have two HR24 and one H24. Thanks.