TRANSMISSION PROBLEM

I HAVE A 1991 NISSAN MAXIMA 4 DOOR WITH 167,000 MILES AND AN AUTOMATIC TRANSMISSION. MY TRANSMISSION WONT DO ANYTHING IN ANY FORWARD GEARS. THIS HAPPENED WHEN GOING HOME ONE DAY AND I SLOWED DOWN AND TURNED A CORNER AND IT JUST ACTED LIKE IT WAS IN NUETRAL. WHEN I PULLED OVER I PUT IT INTO REVERSE AND BACKED IT OFF THE STREET AND INTO A PARKING LOT AND REVERSE WORKS JUST FINE, BUT IT WILL NOT MOVE IN ANY FORWARD GEAR. THERE DIDNT SEEM TO BE ANY SLIPPING OR ANYTHING PRIOR TO THIS, ALTHOUGH ONCE BEFORE THIS WHILE I WAS PULLING INTO A PARKING SPACE IT ACTED THE SAME WAY. I PUT IT INTO PARK AND SHIFTED INTO DRIVE AND IT WHENT INTO GEAR AS IF THERE WAS NOTHING WRONG WITH IT. DOES IT SOUND AS IF MY WHOLE TRANSMISSION IS SHOT OR COULD THERE BE SOMETHING ELSE CAUSING THIS?