Re: Fried/shorted out my 6600GT?
On the surface, I wouldn't think so. Now the ATX switch is not like a standard switch. It sends a signal to the mobo instructing it to "turn off", vs. an actual switch that cuts the circuit... Which brings up an imporant point here, and that is turning off the ATX power, doesn't cut power, so if one is gonna work in there, unplug it, or turn it off from a real switch (perhaps on the PSU itself).
But I'm not sure what happened in your case. Only thing I can think of is there was some kind of a voltage spike which came out of the thing when you bumped into the switch, and this voltage spike caused bad things to happen to your card. Now, how it could have caused a voltage spike, perhaps someone else might have an idea, as I'm a bit mystified myself...