Hi Don,
Actually, lets say the situation is the same as before, current flowing from left to right thru the motor. This time, in order to stop the motor, you switch the right hand side contact to its upper position. While the right hand side contact is open can you show me path for the current to circulate?

If you connect a diode from each side of the motor to the positive rail as well there will be a path.

The difference between a normal diode and a "fast switching diode" is not the turn-on-time, it's the turn-off-time or reverese recovery time as it's called.
When the diode is forward biased and conducting current from anode to cathode its PN junction is charged. When the voltage across the diode is reversed this charge needs to be depleted before the diode is actually blocking the current. This means that the diode is actually conducting current backwards for a (very) short time before it starts to block it.

/Henrik.