robotics newbie needing help with an autonomous bot!!!

[jaykwon]

gud day guys! i need help with this project of mine. its my first time to work on a robot, i was planning to make one of them obstacle robots, its supposed to be simple but its been hell. i used a 16f84 pic microcontroller for the brain and a BA6208 motor driver to drive two motors. i used an old rc car body and used switches to bump obstacles then make it move backwards and turn. i made it but for some reason it can't move. it moves if u lift it of the ground and turns when i press on the switches but wen i put it on the ground it just stays put. i know it aint the weight or the motor cuz it moves if i directly plug the motor with its 9V supply. and for some reason my h-bridge (BA6208) kips burning out a few minutes after i turn it on. can anyone give me any suggestions or answers as to why this happens. thanks!