I just wanted to add this, as I thought it was interesting reading, and I've never found another site that quiet spells it out like this.
It's not completely related to your problem, but it dabbles a little bit into understanding what to do when a cat does that. It's an article from here on aggression, but even though your cat isn't trying to kill you, it IS telling you, "I don't trust you down there, so back off lady!"
Asim does the same thing at times, sometimes he likes belly rubs other's not. He's a very playful cat, he's always been very gentle when he does "bite" or use his paws on me. But when I can tell he's starting to get out of hand with the belly rub aggression and he has my hand wrapped up in his paws and his mouth gently on my hand I just say "alright Asim, no more, this isn't fun." He just looks up at me and then lets me go, and I find something un Asim related to do for a while. http://www.thecatsite.com/behavior/aggression3.html