Try sending them to the lot by taxi and see what happens.
Very interesting. I went to a new Sim and had her call a taxi. Took her to a DT lot and all was fine. Had her take a taxi to the lot that would not load previously and all was fine. Took her home and had her drive her car DT and all was fine.
Went back to my original Sim that had problems and had him take a taxi DT and all was fine. Took him home and had him drive DT to the same lot that would not load before. (I was ready to blame my problems on the Smord truck at this point) It loaded fine.
Went to yet another new Sim. Had her try to drive DT, lot would not load.
So, I have decided that I will have to take all Sims DT in a taxi before I can take them in their car/truck. What a PITA.
Thanks, simmiecal.