Aother Wild stab in the Dark here, but is it Ride Hieght?
Theres only two drivers that i can think of who have been DQed, after winnig the race and they are M Schumacher in 94 and Senna 89, The winner of the latter lead laps during the race, but im not so sure about Schmis race though.
He got DQed because the skid block was worn too much indicating that the ride hieght was too low, perhaps this happened with the other two Drivers