My HR10-250 was installed on 1/18. I hooked up the optical cable late last week, and I'm having problems too. On my receiver, I was using the optical port for the DVD player, and I never had a problem.
I do notice that if I hit replay, I usually don't get the drop out. So, I'm wondering if there's a problem with the Tivo. I know the cable is seated well. I see a red glow at the receiver end, but I've not stared at it looking for a blink.
If anyone figured out a fix or learns more info, please post it.