wyrre,
not sure if this will help anything, but have you turned your ignition on and everything be ok, and then closed the door, or open and close the hood to see if this vibration shuts things off? or even shake the battery to see if things shut off?

in my amigo, i had a post clamp on my battery that even though it was tight, it would sometimes not start, but open the hood, push on the post, or try to twist the clamp on there tighter, (even though it wouldnt move) and boom, it would start.
i know, its not much help, but thought i would throw it out there. i think i eventually changed my post clamps, and the problem dissappered.
maybe check your post for cracking, or loose clamp,
sorry, thats all i got........