Rod,
Josh says he hears the fuel pump prime before he cranks it both when it starts and when it fails.
Relays in back of glove box dropping out (but not always!) suggest a voltage drop somewhere - bad connection, high resistance link?. Couldn't that throw everything off and the ECM would tell "DON'T START"?
mjfdesigns post which resulted in coolant sensor reads like a different problem, IMHO.
Oil pressure sensor and fusible links sound like low cost things to try next.
Also need to confirm (with tester) if spark continues present when failure occurs.