Alt Tab resulting in black screen forcing computer restart

Twice today I have gotten this issue so I presume it is a result of a recent update.

Mid game (summoner's rift) I would alt tab to another window, chrome to change music for example, and I would alt tab back to league to return to my game. It would result in a black screen. The black screen would remain on top of everything so that I could not for example access the desktop.

The black screen would also not be closeable. The taskbar remains accessible. Task manager can be pulled up but since I can't access the actual windowed interface, I can't force close the black league screen. Alt F4 does not force close this screen. Window previews DO override the black screen being on top, but it's just a preview so I can't do anything with it. NOT all alt tabs results in this behavior. I alt tabbed multiple times in that last game and it just eventually happened.

This is on a windows 8.1 system. Since I can't do anything with the black screen, it forces me to restart the entire computer. Can not confirm if audio is still going in game as the audio was muted but pandora continued to play as normal. Non-league programs can be opened and closed as normal. Alt tab to change music is a pretty common thing for me so this must have happened within the last patch or two as I have not experienced this before.