6850 destroyed motherboards?

So i bought a 'new' 6850 (2nd hand but still all packed and un-used). Put it in my comp; no display. Then tried it in my bro's comp; no display. The worst part: now both computers show no display, regardless of which video card I use. They turn on but there's no sign of video signal. Since my bro's comp was brand new I had to return the motherboard (tried different PSUs (this includes a new one by Corsair), memory sticks etc. on both computers) and im left not knowing what to do with this card. I'm afraid im gonna screw up another mobo with it, i want to make things 100% sure though...

The point here is that both computers had display and stability problems the days before. Is there another way to test this card?

KKOPPI said:

The point here is that both computers had display and stability problems the days before. Is there another way to test this card?

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So both computers had display problems before you tried a new card and the new card did not fix the problem... Is that what you are saying?

If you had two boards go down in the same house I'd bet you guys had a power surge or something like a lightning strike.

Did the boards POST at all?

I dont think so. All the fans worked though.
But I should have stated it like this: The fact that the board stability problems occured keeps me from throwing away the card. I already gave away my own board (im about to buy a new one) and my bro's board may be replaced. But now im not 100% sure if my card is indeed a motherboard killer. Sounds very improbable to me.