Client wants to re-install first time run?

When I go to launch League, it tries to start installing the client. I cancel/close the setup, re-open the shortcut to League and it launches as normal again. It will keep launching as normal for the rest of the day if I close and restart it.

But the following day, or next time I play league (days later), it tries to start installing again, so I have to cancel the install and re-open again.

This is not a huge inconvenience or anything, but it's rather annoying. Does anyone else have this problem? It happens on both my computers (in different towns/ISPs). Is it both my computers, or my account, or a common thing with other people?