Blown A/T Fuse in 3000GT

I own a 1992 Mitsubishi 3000GT Automatic and Ive had a reoccuring problem for the past few weeks. Whenever I put the car in reverse, the Automatic Tranmission Fuse blows. Once this happens, all power to the tranny is lost and Im basically stuck without overdrive. Can anyone tell me why this keeps happening or what I need to do to fix this?