Just got error reports saying a language file is missing and to reinstall when switching from the adobe AIR client to the actual game itself, causing it to crash.
1. created a custom gamee , went through champ select as usual.
2. locked in, as the game switches error messages come up
3. "summoning" screen briefly flashes on screen, another error message saying game asset "morgana" is missing
4. client is fine but the game itself doesn't run, can relaunch the client and get up to this point again
EDIT: Does NOT occur in normal NA client. only PBE