OK, whats going on is the passive heatsink vents to the atmosphere and relies on good airflow to remove the heated air, instead of doing this your fans are forcing the hot air to "pool" inside the case, the cpu fan also can't disperse heat because of the heated interior of the case, they all get hotter, the heat has nowhere to go so they get hotter still until it finally crashes.
Flip both those fans over so they vent out of the case then check your temps while running prime95 small fft's once more, I'm sure you'll see a great improvement.
I'm also not a fan of cases on carpet, you should at least have a board or something between the carpet and the case.