Locals+VIP 612+time = no signal?

[Porcelon]

New subscriber here. My setup:
Dish 200+Silver HD + locals, and the VIP612 box

Everything works great except after a few hours I can't watch OTA locals through the box tuner. This is important because Dish doesn't cover (or didn't add) them all as HD channels, even though most have HD prpgramming (Madison, WI).

I've watched the signal strength go from 85 down to zero, this happens when the box has been on for 5-6 hours. If I turn it off and on the problem goes away for a little while. I know I am still getting good signal because I switch to my tv tuner and I get all bars, and I haven't moved my antenna.

I tried grounding the box with my fingers on a screw on the back of the sat box, but there was no change.

Maybe it's heating up too much? any thoughts?

Thanks,
Matt