Well, I have had the chance to take a close peek inside about 3 different broken 360's and the problem in EVERY SINGLE ONE (red ringing) was the heatsinks were really loose. The little X clamps underneath the Motherboard were like twisted and soft, kinda like when you take a paper clip and twist it.
I then hopped online and found a site that sells these bolts and spacers to replace those crappy X clamp things. Well, I ordered a few and replaced the 360s with the bolts and they all worked fine after that!
I then traded my current year old 360 into gamestop, bought a new one and popped it open and replaced the clamps with the bolts. No problems in the past 4 months since I bought it. Microsoft needs to REALLY look into those clamp things.