I have a 1982 Toyota Supra P-Type. Five speed. I was driving today and as I downshifted from 3rd to 2nd I noticed that it was very difficult to move the shifter into 2nd. I came to a complete stop and was then unable to shift into any gear. A cop pushed me into a nearby parking lot. I went to work for a few hours, came back, called AAA without touching my car, and the AAA guy started it up and it drove fine. Does anybody have any idea what went wrong and what I can do to prevent it?