A few quick thoughts:
Do a power cycle on the problem receiver. Maybe even a full-blown reset. Don't know if a reset will require to you reauthorize the receiver, but if it does, you can do that on-line.
Try swapping the two receivers and see if the problem moves to the other TV.
Check the voltages at the power plug to make sure you're getting a full 120v for the receiver. Don't think that would do it, but worth a quick check.
Is your DVR hard drive really full? Sometimes when it is, the recording gets fragmented so badly the receiver can't reassemble it fast enough - especially if the DVR is also recording something else at the same time.
I don't know if DirecTV cares if you've taken your receivers from home. If they don't, you might want to get a service call. My guess is they'd just give you a new receiver, but also don't know about that. Personally, I like it best when DirecTV stays away. :)
al