My airports are in good shape ( all check out fine with AFCAD fault finder...parking spots are fine, etc.) but at KATL all the jets vanish after landing and going down the runway a bit. The prop planes don't do this. There's lots of available parking of the correct size. I'll probably see this at other airports too; some of them are very empty despite the fact that I have lots of flightplans for them. This happens with my own flightplans and PAI flightplans

Are you using overlays with KATL? If so, the jets may be contacting the overlay for GA, and not finding any appropriate parking. Or they contact the right overlay, but they're on the wrong runway and can't get to the parking. This might happen if you've isolated the overlays by breaking the taxiways that go between them.Do departing aircraft work OK? That's a good test for parking space radius. Also, have you split the runways for takeoff-only and landing-only? If so, you might be missing connections from the landing-only runway. Remember, the Fault Finder in AFCAD, which is a GREAT new feature, won't find "missing" taxiways - only isolated nodes and parking.