1999 Suburban won't start suddenly

My wife went out to start our 99 Suburban but it will not fire. It ran fine earlier this morning but after sitting for just over an hour it will only turn over but not fire. I can hear the fuel pump run when the key is turned on and after an attempt to start. I heard soem very low pops a couple of time when I attempted to start it and stepped on the gas pedal. Any ideas?

UPDATE:
After let the Suburban sit for a few hours it suddenly started and is running fine. Have been afraid to cut it off for fear of not getting it started again. Went by the local Goodyear and explained everything to them but they said that they do not have a clue and that I should just drive it around and call them if it will not start again.

I would rather have some idea of what is going on if anyone else has gone through this or heard of the same.

Leave the key in the "ON" position for 5-8 minutes. the computer will reset the password, after shutting off the vehicle, it will restart.

TRY THIS

GM came out with the Passlock system on full size trucks in 1998. My oldest son just went through this about 3 mo. ago on his 1998 K2500. This procedure does work:
Here is a link to the procedure:http://www.fullsizechevy.com/forums/general-discussion/performance/164702-gm-computer-relearn-procedure-including-crankshaft-relearn.html