I think I am in the same boat as you. I just got a 990, and I am starting to have issues with the video. I too use a 35' cable along with the 6' cables on the HD box and DVD player. (I used 6' before I moved all the equipment this weekend.)
I think that the 1080p drop out makes sense. That has a much higher bandwidth usage that 1080i or 720p, so it is a lot more info to get thru an already iffy length.
I ordered my cables off a website that is actually very cheap, but good quaality if you want to try a shorter cable. (ehdmi.com)