Alt-Tab disables game

I have not had this issue until the recent update. Alt-Tab now disables the game. The screen goes black when going back into the game, for about 15 seconds. After that, you are disconnected but can see everything.

I was playing an ARAM match recently. I Alt-Tabbed to change the music I was listening to. After attempting to return to the game, all I got was a black screen. This lasted a while. When the map finally loaded, I could not click or cast any spells, and was walking harmlessly back to the fountain. As I was the last hope before they destroyed our inhibitor (it would have been a 1v2 only), this was a game changer. Since I couldn't do anything whatsoever, they easily destroyed our turret and me, then won.