[CLIENT] Game failed to retrieve data from server while changing masteries & accepting a ranked game

Hi Riot,

Everything is stated in the title - I was waiting for the ranked game to tag on, all the while changing some little things in masteries, when the game finally popped up. I clicked on "Accept", I saw everybody accepting, and right when the 10 people accepted, the client was all black. After like 10 secs, it asked me to save the changes I made in masteries, I clicked "Yes", and then the following messaged appeared: "Game failed to retrieve data from server. Please report (...)", and I don't remember the end of it. I was able to click on "Cancel", and the screen basically remained black.

I waited for 1 / 2 min, and I heard that I had dodged the champ select of the game I was in. Kind of annoying bug (...)

Thanks for your attention.

Cheers Riot!