I'll check with him the exact versions, but I had helped him build the HTPC and we updated everything (drivers) at the time it was built (roughly back in July). I believe he is running the latest Prime official firmware. I asked about pixelization and he said he didn't see anything that he hadn't seen before having a cablebox.
That last statement is key. When I first noticed the pixelization I thought it was normal cable signal-type pixelization. After I got my tuner reliability improved and ditched all my cable boxes I started optimizing my signal strength in hopes of reducing or eliminating it.
After getting my signal strength where it should be and still seeing pixelization I started looking elsewhere and found the packet loss. Now that I have my PCs fixed at 100Mbps I see basically ZERO pixelization, much better than with my cable boxes. To some the pixelization I was seeing might seem normal if you're used to a sub-par cable signal.
He's not on AVS and I know his life is a bit busy at the moment so I don't want to bug him too much, but if there is anything specific you'd want to know I can try.
No, that's OK. I'd love confirmation of the BIOS & driver versions he's using, plus the results of a packet loss test, but I know what a busy life is like and I appreciate the input you did provide.