No. Mercury-Redstone 1 had a launch failure after ignition and launch:

Video: http://www.youtube.com/watch?v=7O4V7JfeTSU

Description: http://en.wikipedia.org/wiki/Mercury-Redstone_1#Causes_of_th...

No, SpaceX themselves have done it several times, and I'm about 90% sure there's prior precedent as well. It's a theoretical capability of any liquid-fueled rocket, assuming an adequate hold-down system.

Edit: Looks like Ariane 5 has similar systems on its main engine, but it also uses solid rocket boosters, which can't be shut down once started. http://www.space.com/11264-rocket-launch-aborts-engine-malfu...