[CRASH] Crashing at start of ARAM

Every 10-15 games or so of ARAM, my client freezes. It's at 100% loaded, but the circle in the top left stops and I can't minimize the game. The only option is to alt-ctrl-del, sign out of Windows, then sign back in and relaunch LoL. If I catch it right away it doesn't impact the game much; my computer is fast enough that it only takes about 30 seconds to go from signing out all the way back into the game.

However, on top of that obviously not being something I should have to deal with even if I can fix the problem quickly, this happens a fair bit to other people as well. I used to get pissed off at how many people wouldn't be there for a game until it started happening to me. It impacts a fair number of games, on one side or the other—even if the person restarts and comes back, if their computer is slow or they don't realize it's happening it can take several minutes, at which point the game may be mostly decided.

I haven't found a specific way to reproduce this issue. Mostly I'm reporting this because it seems widespread and maybe it's a known problem with a known fix.