Of course, if the boot is freezing when the BIOS is checking the controller circuitry (long before it checks the drives), then maybe it could happen before the video bios announces itself... (I dunno). In that case it could be, for example, a bad motherboard, low power, or the wrong thing connected to the controller.
Anyway, you've got a lot of stuff to check. Might hit it on our first round of suggestions.