If Pascal's mugger was a force of nature - a new theory of physics, maybe - then the case for keeping to expected utility maximisation may be quite strong.
There's still the failure of convergence. If the theory that made you think that it would be a good idea to accept Pascal's mugging tells you to sum an infinite series, and that infinite series diverges, then the theory is wrong.
The convergence can be solved using the arguments I presented in: http://lesswrong.com/lw/giu/naturalism_versus_unbounded_or_unmaximisable/
Essentially, take advantage of the fact that we are finite state probabilistic machines (or analogous to that), and therefore there is a maximum to the number of choices we can expect to make. So our option set is actually finite (though brutally large).
There are two separate reasons to reject Pascal's mugger's demands. The first one is if you have a system of priors or a method of updating that precluded you from going along with the deal. The second reason is that if it becomes known that you accept Pascal's mugger situations, people are going to seek you out and take advantage of you.
I think it's useful to keep the two reasons very separate. If Pascal's mugger was a force of nature - a new theory of physics, maybe - then the case for keeping to expected utility maximisation may be quite strong. But when there are opponents, everything gets much more complicated - which is why game theory has thousands of published research papers, while expected utility maximisation is taught in passing in other subjects.
But does this really affect the argument? It means that someone approaching you with a Pascal's mugging today is much less likely to be honest (and much more likely to have simply read about it on Less Wrong). But that's a relatively small shift in probability, in an area where the number are already so huge/tiny.
Nevertheless, it seems that "reject Pascal's muggings (and other easily exploitable gambles)" may be a reasonable position to take, even if you agreed with the expected utility calculation. First, of course, you would gain that you reject all the human attempts to exploit you. But there's another dynamic: the "Lords of the Matrix" are players too. They propose certain deals to you for certain reasons, and fail to propose them to you for other reasons. We can model three kinds of lords:
Precommitting to rejecting the mugging burns you only with the foolish lords. The sadistic lords won't offer an acceptable deal anyway, and the testing lords will offer you a better deal if you've made such a precommitment. So the gain is the loss with (some of) the foolish lords versus a gain with the testing lords. Depending on your probability distribution over the lord types, this can be a reasonable thing to do, even if you would accept the impersonal version of the mugging.