I did something similar a week ago coming down our icy, rutted driveway on my fixed gear. I was modulating speed coming around the corner with my rear wheel when I started sliding until my front wheel was still pointing downhill but the rest of the bike was almost perpendicular to the direction of the slope. Amazingly I didn't crash, but I've fallen plenty of times on that driveway this winter. Kind of a crappy way to start a ride.