02 Trailblazer cranks, but doesn't start

My 02' Trailblazer runs great but sometimes after it has been running a while, I'll shut it off. If I try starting it, it just cranks over, sputters, and won't start. I can usually let it sit an hour or so (usually) and it will start up and run fine. I've replaced the fuel pump and fuel relay. I had a diagnostics test run, and it showed no errors. However, the fuel pump kicks on when it throws these fits, but there was no fuel pressure to the motor. I'm wondering if it could be a security issue????? Anyway, several dealerships are puzzled, as well as I. Any ideas?

I would check if the fp regulator gets stuck and returns fuel pressure, hence no start. Does the pump prime when the condition occurs?