This happened to me a few moments ago! Ugh! So frustrating! I was in normal draft pick for Summoner's Rift, everything was going fine until the loading screen. Once the loading screen pops up, it looks normal, but doesn't load anyone's champ picture and crashes. So I send the error report and try to reconnect. Everytime I tried to reconnect, it decides to show up a black screen and doesn't do anything. So, I kept trying to hit 'esc' and then reconnect. After a few tries, it gets back to the loading screen and starts loading my champ to about 50% and then it crashes each time. I am not sure if anyone ever got into that game or not. So, I got to the point where I exited through the task manager, pulled up the client, and then it said that there was corrupt data and that the files needed to be fixed. I hit "no" and rebooted my computer, but when I pulled up the client again, it told me the same exact thing, that the "data was corrupt and files needed to be fixed" so I hit "ok". It is applying patches and I guess trying to fix what may have gone wrong.
I wonder if this is a widespread problem, but I can say that it isn't only you because it happened to me, too!
After it did it's "fix", it still wanted me to reconnect, and I did - but I wasn't able to help my team at that point =( not fair.