transmission stuck in neutral

my 1986 b2000 was shifting well and then as i put it in neutral it got stuck and would not budge as i tried to get into first. in fact it froze stuck in neutral? actually a little to the left as the shift pattern moves toward first. i was able to push the car out of traffic but i am unable to move the shifter? the truck has 225,000 miles but up until the point it froze it shifted without any problems? need a clue. thanks edsel...