It's been too long since I've flashed a console so my memory is failing is this regard, but I believe the issue is caused by the wrong SMC. Basically, after you flashed the console, if you didn't unplug it from the wall, some of the code that was in the NAND previously can still be used. If you've flashed an image with some bad parts, it might not show initially because the console will still be using it from the previous image. When you unplugged the console, the console was cleared and had to load from the NAND again, causing it to fail to boot.
tl;dr: you flashed an incorrect image to your console and will need to hook up a programmer to fix it.