Level 6, and can't select any champions

This bug occurs if you:

1. Do not own any champions
2. Leveled up their summoner level from 5 to 6
3. Did not close the client after leveling up

The result is: Every time you try to pick a champion in Champion Select, it will tell you an error occurred, and won't let you pick anything

I've already lost about an hour from this. Please fix it.