While cruising at 7000 feet, the pilot experienced a loss of power on the right engine. The pilot requested assistance from Jacksonville Center, and was vectored to Cochran Airport. The pilot established an approach to the airport but was unable to lower the wing flaps. Apparently, after the landing gear was extended, there was not enough hydraulic pressure available to lower the wing flaps. The only hydraulic pump was installed on the right engine. The pilot lost directional control during the landing rollout, and the airplane veered off the right side of the runway into a ditch. The pilot stated that heavy left braking was used, but failed to correct the rightward drift. According to the flight manual, the pilot should use engine power and braking to maintain directional control during the emergency landing. Examination of the airplane disclosed that the right fuel shutoff valve had failed and fuel was shut off to the right engine. Additionally, the right wing spar was repaired prior to restoring the airplane to a full airworthy status.