Mostly my fade spots would be the two areas where I see double braking zones back-to-back going the CCW direction: just before Diamond's Edge, and just before the Bus Stop. In both cases you've got a hard hit on the brakes at the end of a straight to come down from e.g. ~115 -> ~80, then a very brief steady throttle, then another brake hit all the way down to ~45 or so in a very short distance (give or take whatever for car/skill). Whenever I've gotten fade on the track and/or ice-mode problems, it's usually the second brake zone in one of those two spots.
(for those unfamiliar with this track, here's a PDF with the major corner names labeled:
http://msrhouston.com/pdfs/RoadCourse-corners.pdf . The first case I'm talking about the braking zones and just before and just after Turn 3 going into Diamond's Edge, and the other pair straddles Turn 7 heading down into Bus Stop).
Here's a video of me going through that sequence:
MSR Houston CCW - TDE 20120421 - 370Z - YouTube. The second pair at the end of the back straight looks a lot tamer in that video than it generally is, as on this session I was braking earlier and softer than usual.