[CLIENT] Client crashes and then when reopening won't accept password

Before my games, during the loading screen or even the champion selection the game would crash. When I try to open it to load into the game it says that the client was restored to another version so I can play, but then it won't accept my password, no matter how many times I restart the client and the computer. This is really annoying, as I already lost points for this happening in ranked games. What can I do about it? At first the problem solved by restarting the computer but not anymore. After a while I restart the client, but then it would redownload the whole patch (1.3 gb) which is really annoying, and after that I can play, but I'm sure the problem will come back.

Thanks, please help!