Just to complete this, the H20 I have is a 100. (My H20-600 died a hot death years ago).
At any rate, I ended up calling DirecTV, went through the steps with them. They sent "information" to the receiver (assume that was a reauthorization), had me RBR it, unplug the coax from the wall jack, tune to the satellite test channels (in the 9000 range - forget the exact numbers). Long story short, nothing worked. Finally ended up scheduling a service call.
Then, just for the heck of it, I pulled out the power cord from the back of the receiver and let it go through the reset process again (about the 5th time it had been reset at least) and lo and behold, the HD channels came back!
I have no idea what the problem was or if pulling the plug fixed it, but am happy to have the HD channels back since this receiver is on my main viewing TV (and the Justified Season 3 premiere is tonight!)
Thanks to all for the suggestions and jumping in so quickly to help. This is why DBSTalk is such a great forum!