Electronic anti-theft sysytem

My 1997 Chrysler T & C has an automatic anti-theft system that engages every time the car is locked. However sometimes, randomly, it will not disengage when I unlock the car and will not allow the engine to run. It cranks over fine but will not run. After waiting 24 hours it will crank and run fine.Any ideas on how to fix or deal more effectively with this problem will be greatly appreciated.

I would assume the disarming process is internal to the alarm system and if it is, you may have to replace the alarm system to fix it.