Well, the nice support lady just told me that the problem is with the broadcasts, and DirecTV is "working to resolve it". She said that a large number of receivers have been replaced due to dropouts, but they now feel that it's an issue with the broadcasts from DirecTV.
On the surface, it would seem that this problem only affects certain receivers, which seems odd. Time will tell I guess. but considering that I paid them around $500 for this system, I hope it gets "resolved" without me having to RMA several receivers. BTW, I ran signal strength on all 3 satellites, and all transponders are at 96 or above.