Problem solved!! For some reason, both the original installed AFCAD and my modification (made from original but with CW runways activated and extra parking) had all runways set to zero width. In other words, there were runway link paths but no wide grey strip of runway. I set the runway width for each runway (according to the "updated AFCAD" in this forum. The grey runways then appeared in the AFCAD. When I compiled and installed it, all the AI were taking off correctly. Prior to this, they would only take off if they were first to the runway holding position and given immediate clearance for takeoff. If they were number 2 in sequence and given a line up and wait clearance, they would line up but never received the clearance to take off.