Accelerator Stuck problems of the 1999 Toyota Sienna

I am reporting another Toyota sticky accelerator pedal. Our 1999 Sienna minivan has had 3 incidents of stuck accelerator, the most recent was Jan. 21, 2010. I believe it has become "stuck" between 40 and 45mph. Other incidents were in summer (cannot remember date) and October 2009. The 1st incident was brief and corrected quickly by pushing down on the pedal to "free it", the 2nd incident required braking and putting the car in neutral and shoving the pedal with my foot to the left and right to free it up. I was able to drive the car to the shoulder, turned the car off and then the pedal seemed to work ok, although a bit sluggish response. Our mechanic fixed the throttle body and the car has not had another incident until last week. The most recent incident was more harrowing in that there was not much room to maneuver the car since we were headed for lots of cars stopped at a traffic light. I tried to slow the car by braking hard with the left foot and shoving the accelerator. Pedal down and side to side while in neutral but this did not work quickly like the October incident. I was able to pull over to a shoulder before crashing but it took much longer for the car to stop this time, and I actually threw the car in park to stop the car! I turned off the car and after a few minutes, was composed enough to drive it. Our dealer will check the car Jan 29. The floor mat does not appear to be involved jamming into the pedal, so it is probably a mechanical "catch" that is getting hung up when the pedal is down a certain distance. We thought the safety gurus would want to know. Luckily no crashes have occurred yet!.