Clan War when changing sides.

MaybeCookie

Can anyone help me with this, well to the basic my CF keeps lagging when i start a game it doesnt load to the screen but it goes top left of my screen and all i see is black. Also when sometimes it loads i play a clan war and then when im done it doesnt load the game outcome anymore but it just stays black and doesnt load to next half so what do i do. I dont think its the PC problem because it used to work on the PC before i had to reinstall. Any help anyone?