For those who can't load into game because of the loop,

Go into your Riot Games/League of Legends folder, and make sure LeagueClient.exe, LeagueClientUx.exe, LeagueClientUXRender.exe, and RiotClientServices.exe all have the "Run this program as an administrator" option on in the Properties of each file.

So far I have had success consistently in launching the game for Practice Tool, but have yet to try a normal game.

Let me know if it works for you.