What type of machine is it installed in? From your description, it sounds like the card isn't fully seated into processor slot... you should take it out and try re-inserting it. You sometimes have to use a considerable amount of force to seat the card properly, so don't be afraid to really push the card in very firmly (but, with a gentle firmness...)
It is also possible to ruin your card if try to start it up when it isn't seated properly, but it isn't very common. just double check everything before you boot up.