It just started this late yesterday afternoon after I got off from work and the dealership was closed. I haven't had a chance to ask them yet. But, I was hoping this was something simple that maybe was common to these SUV's. I didn't really want them to make me out to be an idiot for taking it in for a thumping noise.
So, I thought I'd check with all of you first since you might know more about it than me.

Is this a serious problem? I thought it might be the gas since I've only put one tank of gas in it and it was the night before it started making the noise. Maybe I got bad gas? Can water in the tank cause this kind of noise?