Craftsman Riding mower #917.270912 dies when I let off clutch?

My Craftsman riding mower starts & runs great. As soon as I let off the clutch or start to engage the blade, the engine dies. It's definitely a switch problem, but I don't know where. I bypassed the seat switch, even though it checks good with a meter. I bypassed the clutch switch, but it died as soon as I engaged the blade. I bypassed the blade switch, but it died as soon as I let off the clutch. Could the ignition switch have anything to do with it? There are definitley no shorted wires anywhere. I disconnected the ground from the seat switch under the seat & everything works great, except you can't turn the engine off then. HELP!! I'm going crazy!