take the cover off the motor control box and locate the main relay, there are 2 small blue wires (and 2 thicker ones) connecting the relay to the board, pull one of these off the connector and re-apply the power, if the motor still runs then the relay has welded its contacts together, if this is the case, check the diode at the top of the board, usually these blow if you push the c5 backwards too fast and as a result the relay arcs and somtimes sticks shut, you can sometimes salvage the relay by seperating the contacts and cleaning them up with a piece of fine emery paper and replacing the diode, Karl should have some of these. If this isnt the problem, look for a faulty switch or a short circuitin the switch line.
Hope that helps