how can my ford mondeo 1.8 lx 16v 1995 model be fixed?

when i unlock the driver side or the passanger side door of my mondeo the red sensor light stays on and keeps flashing and i get a clicking noise coming from the ignition side and it lasts for about 2 mins. Then when i start the car and then switch off the ignition the car still keeps running and i can take the keys out off the ignition so i have to stall the car to stop the engine. but if i open the boot first before i open the driver side door it dosen't do it. So can anyone help me out with this one please thanks.