Yes, mabe the card has problems.
Do you have any other cards in the other two x16 slots?
While normally running the graphics card in the first slot is the preferred method, have you tried running it alone in slot 2?
Note that I agree with the Chief, that card should run just as fast in an x8 slot as an x16 slot - so you should see little real difference. But still it would be nice to have system working at spec.