Stalls after topping off?

This is a question on my dad's '00 SL500. He says after he goes to the gas station and he tops off the tank the car will sputter and almost die when he slows down to turn at an intersection and one time his car just died out on the freeway. He say this only happens after he tops off. Of course I told him to stop topping it off but he said it's only being doing it recently. What could the problem be? I would imagine something in the fuel system doesn't like being topped off or perhaps it isn't even related. Has anyone else had problems with stalling/sputtering after filling up? I think I've read about warm start problems so maybe it's that because cold start is fine.
Thanks in advance.