HELP!!!

[Vettever]

02 ZO6 16,000 miles. Every once in a while (like maybe once every 2 months) it fails to start. Everything works, acts like the neutral switch is not working. I replaced the battery after the first time it did it and it has happened about 3 or 4 times since. I changed keys, thought the chip could be the problem but it has happened again. It has always started after a bunch of tries and has not let me down yet but sooner or later I'll be calling for a tow truck. If I take it to the dealer he will have it for a while and give it back with a big bill and "couldn't find nothing wrong". Anybody got any ideas?
Thanks
Joe