Due to me screwing up yesterday, this post is a bit out of order. Sorry if it causes confusion. Post #4 above was in response to the following comment.
My first suspicion then would be a coolant temperature sensor that is out of range and causing a really rich conditions. The next time this happens you should try holding the accelerator completely to the floor while trying to start the engine. This will put the vehicle in "clear flood" mode and shut off the fuel injector pulsing. If it starts this way then you can have a pretty high confidence that you're correct and the engine is flooding. Then you get to start the troubleshooting to figure out why. If the engine still acts flooded then you might have a leaky fuel injector that is letting too much fuel past.
Do you have a scan tool that you can use to check the Short Term and Long Term Fuel Trim (STFT and LTFT) values?
-Rod