Not enough voltage, too much heat, or the card is borked
I have a borked sapphire, thank god its under warranty, that bsod on 3 dif rigs. One it bsod at start up, the 2nd one as soon as it starts mining, and all of them bsod when reinstalling drivers. These are the symptoms of a borked card.
![Cheesy](https://bitcointalk.org/Smileys/default/cheesy.gif)
test in multiple systems and you can be sure.