[Art Vigil]

Mine does that too - especially on washboard roads - it shuts off after a few days of driving as long as I don't repeat the incident. I believe it's caused by a malfunction of the "rough road" sensor.
I know that my vehicle has a recall related to the sensor that I haven't bothered to get fixed yet, you might check with one of the local dealers to see if yours does as well.
The purpose of the sensor is explained better by Alan Dobbs below (taken from the D90 source FAQ):

Subject: Re: [D90] Anybody know about the Rough Road sensor?

Alan Dobbs wrote:
> The function is just to let the ECU that you are in a off-road condition
> I.e. one wheel spinning. This prevents a check engine light from
> illuminating from a small misfire or a minor hick-up type condition
Close. It lets the ECU know that wheel speed varies so that it doesn't pickup that variation through the crank sensor and interpret it as a misfire and hence illuminate the MIL. Off road speed variations are sufficient to vary the crank rotational speed. Since the primary monitoring for a misfire is done at the flywheel with the crank sensor alternate causes of speed variation need to be monitored.

 

[Art Vigil]

Dave you RULE! I just tripped my light again also.
See you Saturday, I guess I owe you a beer - you're a 'stout' guy, right?