When it comes to source components, there's a huge range of variation, particularly with cable or satellite receivers (this is something that all receiver and processor manufacturers struggle with - I just saw a comment from another manufacturer along these same lines a day or so ago). The original problem that was relatively widely experienced with the 970 and 1070 was apparently addressed with the firmware update (based on the fact that nearly everyone found the problem to be resolved), but it is possible that a few people's satellite or cable boxes are just enough out of spec to throw a wrench in the works for the 970 or 1070. The variation from spec could be slight enough to only affect a handful of receivers or processors - it's even possible that an identical satellite or cable box would not exhibit the problem. Would the 990 be better able to cope with the deviation from spec better than the 970? Beats me, but there are a bunch of 990's out there and we haven't heard of anybody having these problems.

Having said all of that, I also want to add that none of it helps when it's your processor and your cable or satellite box that are fighting. I'm sorry, fellas.