Only thing i can suggest would be to make sure that the motor sensing setting (red LED) is at it's stock setting of 2, but without working LEDs you are pretty much stuffed. change the batteries to make sure its not just flat batteries with not enough power to light up the LEDs (or spin the motor) then report back.
EDIT: Does the motor spin forward at all? or does it only stop working when you press the backward button to unjam it?