LSU/Arkansas Clock Situation

[Fan10]

Can anyone explain this clock situation? With 1:40 to go on a play where the ball carrier was tackled inbounds, Arkansas had an injured player. After he was helped off, the clock started on the snap. You could see Bobby Petrino saying, "That's bull ----," and based on what I saw, quite frankly, I agree. Did I miss something that would have caused it to start on the snap? It wound up not mattering because LSU fumbled on the ensuing possession, but it could have given LSU 25 extra seconds.