2003 Ford Taurus my car suddenly would not move

i was driving my 2003 ford taurus from work. i stopped at a stop sign and go, just like what i do daily. everything was ok. when i start to go at that stop sign, i found the RPM panel goes over 3000 rpm and my car wouls not move anyway. I tried shift gears to R, D. the car would not go back and go forward. I shifted the gears to N and pushed it to roadside. by the way, the engine and panel shows no problems. no any warning light is on. i have no idea of it. is it a transimmision problem or other? Thanks a lot. jim