Could be the HPOP. Have you tried unplugging the ICP sensor to see if it starts? Doing this tricks the computer into thinking there is enough pressure coming from the HPOP. If this works, replace the ICP... if not... might be time to look at the HPOP, but the fact that YOU shut it down and it didn't die on it's own, kinda makes me think it's not the HPOP, but then you never know, I've heard of stranger things. Checked your oil level lately?