I love how people magically expect us to know what LoL is...
Anway, fortunatly I know that it is League of Legends.
Try running the game as an administrator, it might require extra permission to access some of the components it needs.
Make sure you have updated your video drivers/DirectX, as the game is realitivly new it might require newish builds of those components to work.
Finally restart your computer, that is always helpful as bugs might cause resources to become locked and so unusuable to other programs.