[CRASH] League is Unplayable

Right now, when I load up the client, everything goes swimmingly. I can buy from the shop, go into ranked, champ select, even get through the loading screen at breakneck speeds with under 40 ping.

Somehow, however, league just loads me into the game, and freezes at about the 3 second mark. Not just my movement, mind you. League has completely eliminated any chance I have to make a change to settings in the game, or to try and lower quality to see if that helps the same computer on which I've been playing this game for two years.

The worst part is this bug popped up during a ranked game. I played for a while, not realizing this was a bug, and it locked me out. I loaded back in, played for another 3 minutes, and it locked me out again. So now I'm stuck here unable to load into even a custom game.

The game is frozen, and so is my computer. It locks up and I have to restart the damn thing to even see my desktop again. I don't know what happened here, but when a computer that's been successfully running league for two years (even as recently as a week ago) stops being able to even get me past the loading screen, there's a fundamental problem, and I can't help but feel that the latest patch is to blame.

I'd be happy to send in any sort of report if that would prove helpful, but I don't know if I can get the info you'd need since league keeps locking me out of my own computer.

EDIT: I'm running League on a Lenovo T450s with Win 10 64 bit OS.