i have the same problem, i login many times and it catch up randomly, this is not the whole story, sometimes the home/profile page/friends are blank or take a long time to load, when i try to play i click on "find match" the button is LOCKED and nothing and i can't leave the party or do anything at all, and sometimes when u re-login you have a ban because you didn't accept (well i was waiting and i didn't receive "match found" message to accept it) (i already been banned for 1 HOUR), and also sometimes i change my champ and i may get a "connection error" message or i see all my friends didn't pick their champs, i change my runes and masteries but it doesn't change and the buttons get BLOCKED, champion select chat not connected, the match has started but your client is stuck in champion select at 0 seconds, all this issue has been reported hundreds of times... and no answer found yet, they ignore? idk
i formatted my whole PC a few months ago, yesterday i was playing fine but the problem came by at night i tried to reinstalled the game fresh today and i still have the problem, and i wasted now 1 hour in a hope to play another match.
in-game is fine... FINE, but client NOT!
this issue come randomly and i have no idea how to fix it, all i can say it's riot side!