Anti theft turned on while driving on 98 Ford Contour

Ok, so for some reason one night when I was driving home from work, my cars anti theft system turned on while I was driving! My steering wheel locked up, and accelerations wouldn't work and my rpm was shooting over 3, and when my car stopped at a red light it would die. What's going on and how do I fix it without spending more than the car is worth at a dealership?