i had the same problem, just got back from the dealership. they stated that the fuel trim was out of wack. they said after filling the tank i should drive for at least 20 min before parking it. they stated that the engine doesnt have time to calculate how much alcohol there is in the fuel.
thing is that i have been getting the same gas from the same company for the past 6-8 months...weird. anyways its working fine now.
i have read on some other forums that this can also cause some smoke to come from the exhaust on start up. i have noticed a slightly blue/gray smoke on startup the other day, we will see if it ceases now that the problem is fixed.