ok. here is a short video of the car "trying" to start. Maybe someone can tell by the sound of what it may be. The battery on my camera was dead, so I had my neighbor (who also has a W126)take this video for me... thats who you see running around. lol.
just click on the pic and it will load from photobucket... you can hear the car will try to start at the end of the cranking, but it stalls back out...
remember this car was starting perfectly until I stopped last night at the gas station and filled it up with gas.

We are going to check for "spark" tomorrow and go from there.