Problem with alienware 15 r3 Cassini

Hi all i've recieve my laptop almost 3 weeks ago and i've a big problem with my ethernet card KILLER e8400. Simply when i put my lan in it dont work, trying to connect but after some seconds the yellow triangle goes away and the computer is not able to connect. 

The lan is working well with other laptops same cable, i've try replacing the drivers with some from alienware download page and also with killer drivers itself. i've also tryed to format and restart from a clean version but nothing worked.

Installing killer driver downloaded from their site has done some help letting me connect with the lan but after some times the connection where not that stable and tonight i've another time the issue.

What can i try??