DGT 6000 Koehler Engine Problem?

I have a Craftsman DGT 6000 graden tractor with a 27hp Koehler engine. I was driving along fine with the mower deck engaged, when the engine abruptly just stopped running. When I turned the key to restart, nothing happens...no clicking noise, nothing. I made sure the mower deck was not engaged, made sure the brake pedal was depressed fully, and even checked the connection for the dead mans switch under the seat. I also checked the 30amp fuse and the connections to the starter. The battery, after several attempts to start is low (9.5 volts). Wiht the key in the on position, I hear a click when I activate the mower deck switch. There is enough battery power to run the lights. Is this simply a low battery problem, or is something else going on here?