Daughter had the same problem with a 2001, V-6 with 30,000. Vehicle engine would turn over all day and not start. Had to have it towed in. There was no prior problems with starting before this happened. They replaced the ignition module in it. No problem with it since. It has been over a year now. The ignition module has something to do with the anti-theft also If I remember. Was fortunate to have the 5 yr warranty still in effect. I think about $170 at GM for the part?
Good luck with your fix. Let us know what it turns out to be.