Saturn Aura XR, excessive crank

I own a 2007 Saturn Aura XR that has 171K total miles on it. I've had it since the summer of 2009 and I've driven it approximately 140K miles. The following problem has plagued me for approximately the last 12 months: Whenever I fill the gas tank, the very next time I try to start the car it doesn't start right up like it usually does but "cranks" quite excessively. After a few tries it finally starts up. To put it concisely -

- car is low on fuel
- engine is turned off
- tank is filled
- attempt to start engine, fails, resulting in abnormal amount of cranking
- 2 or 3 subsequent start attempts are usually needed to start

I've paid quite close attention to the behavioral of the car the past several months. Usually it starts right up with no hesitation whatsoever. The only time it gives me trouble is when I top off the fuel tank, NO OTHER TIME. Seriously, it has never, not once, given me a hard time starting except for when I top it off with fuel. Anyone have any thoughts on what might be going on?