Client Locked Up After Choosing Champion (Ranked)

I was unable to change my runes or masteries after locking in a champion, forcing me to either bring a useless mastery page into a Ranked Game or leave and let my team remake. I chose Option B, because I'm a nice guy. This is the third time it's happened, but the first time I actually got stuck with a bunk setup for a game that mattered.

I'll be more attentive to changing my setup before I lock in, but I hope this isn't something that continues for very long.