The custserv answer sounds like a magic card resolution sequence. Unfortunately, I think that is probably they best they can do for a theoretically open-ended question.
I would say just apply a little bit of consistent logic. When neither opponent chooses to use their AOO with an action that does not draw another AOO, I would probably get tired of it and move to the next initiative order, ruling that the two combatants had drawn themselves to an impasse. Thye are both so good that they fought each other to such a standstill that neither of them achieved anything useful.
I can see where people might get a little upset about that, but I can see two opponents drawing to that conclusion.
Or you could rule it that if you are attempting an action that draws an AOO, and somebody responds with an action that draws an AOO, you cannot respond because you are already engaged in that action.
So somebody tries a disarm and draws an AOO, their adversary responds with a sunder, the first person cannot respond to that AOO because they are already commited to the action. However, an ally certainly could.
Again, I can see some whining coming from that type of decision. But the game is supposed to be fun and it isn't fun when you spend half an hour resolving the stacked AOO's between two opponents before you move to the *real* action for the character so you can finally move to the next person in the initiative sequence.
It doesn't have to follow, however, that it's uninteresting. 
