I have a clifford set up on my cavalier, and i'm wondering if your alarm is set to auto immobilize after a certain number of seconds...
Mine does that, so that if you unlock the car you can get in and start it no problem, but after 15 seconds the alarm will activate the immobilizer again. Then you either lock / unlock the car, or turn the ignition on, and press the lock / unlock button once, and the car wil start...
Sound right?? Or am I barking up the wrong tree here, hehe..