I've had this problem since 2.6.39: my computer won't boot without disabling hyperthreading in the bios. I'm using 3.6.6 now and still have the same problem. The only thing I can add to the description, that it hangs early in the boot process (processing udev).
I think it has to do with this bug, but it hasn't been updated since April. Any ideas?
Earlier kernels (<2.6.39) still boot fine with hyperthreading.