Please see the most recent updates in the "Where did the .com name go?" thread. Posts number 16 and 17.
This first AI left the parking spot on time and headed to the taxiway, then went past the taxiway headed for the hangar across the field. He went through the hangar, across the taxiway and runway, west beyond the airport boundary then began to parallel the runway headed north, continued to taxi about a half mile beyond the runway then turned south, crossed the south end of the runway headed back to it's parking spot, then initiated a perfect turn back to the runway, lined up and took off. That entire process took 25 minutes.
MCX shows the radius to be 5.25Check the radius of the aircraft model that you are using. I have had this problem before and was able to correct it using MCX.

