My clifford concept 650 imobilizer keeps cutting in whilst Im driving?

My clifford concept 650 imobilizer keeps cutting in whilst Im driving. Every 30 seconds I lose all power then I have to arm and disarm on the key thob to start my car again and then 30 secounds later the imobilizer cuts in again.I drive a 1.4 zetec fiesta 1997 and the alarm is wired into the ignition switch.I have checked the wires and connections whitch seem to be all fine and have recently had a new bonnet switch fitted.Apart from this imobilizer fault the alarm work ok?Please help me asap as I need to get to work before I get fire LOL many thanks damsel in distress.