Screen flashes green while watching recordings from DVR

Both of the problems below are with HD channels only.

I have a Cisco 8642HDC DVR. When I watch shows that have been recorded the video sometimes turns green and the audio drops out for a split second. It seems to be worse on some shows than others, for example it is worst on The Daily Show and The Colbert Report.

Another problem I notice is that sometimes when I change the channel to MSNBC or The Weather Channel either my DVR or the non-DVR cable box will briefly say there is no signal on that channel. Usually the picture will come on in a few seconds. If it doesn't, I tune to a nearby channel, like CNN on 1071, then use the down channel button to try to go back to it.

New wiring was installed inside my house when I upgraded to whole home DVR about 12 to 18 months ago. Can a tech check the signal strength?

Thanks.