The problem with logical proofs is that they usually demonstrate a confining lack of imagination. This opening statement, for example, overlooks the possibility of a being with conditional existence. Is it not conceivable that a being might exist only if others believe it exists?
If he were subject to the whims of believers, then he would be, by definition not "all powerful" and not the god discussed in the proof.
I think Godel's proof as I understand it rings valid.
I must admit, I can't read the formal, symbol based version, but from the paraphrasing:
A: Define God as a being that is all powerful.
B(unstated): Define "all powerful" as the ability to do anything, in all possible universes.
C: The probability of such a god existing is non-zero.
D: For any event with a non-zero probability, there is, by definition, a possible universe in which it exists.
E: If a god exists in only one, but not all possible universes, then he is by definition, not "all powerful" and so exists in zero universes.
F: Since we've already concluded that this god exists in at least one possible universe (from C +D), then the conditions for E are not met and this god must exist in all possible universes, including our own.
It's actually a much more clever formulation of the ontological argument, and it's a bit more internally consistent than most. My problem is with the premises B+C. The definition of a being which is all powerful is logically self-contradictory (A rock so big he can't lift it etc) which means there is an actual zero probability that he exists in a possible universe.
However, if there wasn't this problem with the premise, the rest of the logic would work.