[CLIENT] champion pick lobby sometimes becomes a black screen

Sometimes when i am in the champion pick lobby, the lobby shows up on my screen for a split second and then becomes all black. I can still see the chats and the window itself, but everything inside the window is black. I am still in champion select though, because if i dont do anything or quit i still get the 6 minute penalty.

I dont know how to reproduce this, happened to me a few times now in a few days; Not that often.