My mower starts fine but will not go forward or backward and stops whenever I try to engage the blade. What is the likely reason for this malfunction?

Charles, July 2011

Safety switches. If you are not sitting in the seat while the engine is running, and you disengage the brake, it will die. If you are not sitting in the seat and attempt to engage the mower, it will die. If you are sitting in the seat and attempt these things and it dies, there is a problem with the safety switch beneath the seat.

Harry, July 2011