mine dpes this every now and then, if you read your owners manual, it will tell you to take the key out, make sure its clean and wait 3 mins, the VATS system will reset after 3 mins, then if the key is good, it will start. also, GM dealers have a VATS reader too, the can insert a key and see what the chip is and also insert part of it into your switch and read what the code is for the VATS system. mine has done this about 5 times since i had it, just wait 3 mins and try again.