I cant log in

I was ingame and all of a sudden my grame froze with ''attempting to reconnect'' massege and when I restarted my client it just goes black screen and I also think the game ended by now and still wont let me.. any help ? and when the black screen comes on I either get one of these massages , either : '' Unable to connect to the server , please check your connection and reconnect to game'' or '' An unknown directx error has occurred and league of legends cannot start , please make sure the video card is using the latest video drivers from the manufacturer""