Client Keeps Crashing in Champion Select

It's cost me several LP already. It doesn't seem to be bound to any particular thing I'm doing: sometimes it crashes when I change masteries, sometimes it crashes when I lock in my champion, and sometimes it just crashes as soon as the client moves from queue to the opening champion select screen animation. I don't want to lose LP and get leaver penalties just because of a poorly-made client.

EDIT: It also crashes when cancelling queue, and when clicking the shop/crafting/profile icons.