When I plugged my quadzilla stealth in my truck and it said flash error an it wont let me redo it says call the 1888 number but there closed till Monday! It will not let me start the truck turns on radio just wont even try an start just dead.
Leave it for an hour and if no start still ecm may be fried. Im sure theres other things to check, hopefully some others will chime in with some more ideas.
Does it say flash error as soon as you plug it in? If not, return it back to stock. I can't remember right off the top of my head which option you select from the main menu, but there is a way to return to stock without going through the tuning section.
It's probably just the tuner, I had a battery go dead during a bully dog flash, then exactly what you said, they'll have to email you the program again, download it into the tuner, all will be well, just a PITA if they dont have 7day a week support... time to trade in the Zilla for someone with better customer service!