"Automatic" gearbox, reverse problem

What is your question?

the other day i jump started a car. i reversed out of my driveway pulled up to the other car, hooked up the jumper leads up and started it. my mate took both leads of the other car first and accadently shorted out. i jumped back in my car to reverse it back and had no revers at all. but it will drive forward normale and change all 5 gears. revers lights come on, no warning lights on the dash and oil is full. can anyone help with this problem.