These suggestion might help.
hi, this is what i was able to find out online because I have the same problem.
"This problem is caused by the GM Theftlock system which is a security system that whenever the ignition is tampered with the vehicle cuts off fuel and refuses to start. The problem with this system is that there seems to be an issue in many GM vehicles where the system is faulty and constantly is tripping the system at random leaving owners stranded. The quick solution that is located in your owners manual is to leave your key in the "ON" position for approx 10 minutes until the "Security" or "Theft System" light stop blinking and become solid... then turn the key to "OFF" and attempt to restart the vehicle. This has never failed for me, but is becoming annoying. My mother drives a 2004 Grand Am SE1 V6 and it has just started this problem... also I own a 2002 Chevrolet Malibu which started with this problem a few years ago which finally got fixed when I had my mechanic completely replace and re-key my ignition.. This may not be a solution for everyone. But I am glad it worked for me."
I was also informed that you might need to go to your dealer to re-program your "Keyless Entry Remote", because your car thinks that someone is tampering with your vehicule. But you can check to see if the "Keyless Entry Remote" requires a new battery.
