The 75X series of channels are black/no audio (1080i) on one of my two HR20-700 receivers. They come in fine on the one running 0x0263, but nothing on the receiver running 0x0254. I would have posted this in the CE thread if it were the other way around, but I thought it was odd that they're not working on the NR software.
About 5 minutes after discovering this, my NR HR20 rebooted spontaneously, but the channels were still blank after the restart. I have not tried a manual restart (soft or RBR).
I am using an AT-9 with the sidecar removed. Again, they come in fine on the CE receiver--only "problem" I have on both receivers is a 771 message on channel 702. For both PGA and the Olympics mirrored channels, if I turn to the "normal" channel number they come in. Obviously there is no equivalent for the Olympic basketball and soccer channels.