Lol client black overlay bug

From about 6pm-7.15pm AEST I encountered a bug with the lol client where there was a black overlay appearing inside the lol client window. It first popped up when I was in queue for a normal summoners rift game. While in the champion select screen, the overlay was being placed over other players names and champion selected icons. I restarted the client to see if this happens again. I'll also post again if it happens.