Spontaneous Exit Out

starting this patch, my client every once in a while, will simply just end. the window is gone, i cant alt-tab back into it. i have to re log in (the terminate other instance message comes up). My friends say the client displays me as logged in still. This never occurs in game, but i was just interrupted in ranked champ select and was unable to rejoin the lobby despite relogging in time. this has also happened to my friends so it isnt an only me problem. this HAS to be fixed asap.