I assume you have the PCIe connectors plugged in. When you short out the mobo, especially when you get a fireworks display, voltage can go a lot of places, at high amperage, that it's not supposed to go and multiple components can get damaged. You may need to trouble shoot the card in another machine again, or more likely the mobo may be damaged. There is a chance that everything is ok though.
Let me see if I can get the manual for the card and take a look at it.