League of Legends Launcher doesn't open[CLIENT]

I'll start saying that up until yesterday evening i could open it as usual. No Matter what I try to do, the Launcher doesn't open. When I run my game, it flashes the words "League of Legends" on screen, followed by another logo with a loading bar underneath it for a split-second. Then it dissapears and will not show anything else. It shows up in my Task Manager for a second, but then it disappears. I've already tried running it as administrator and disabling my antivirus.. Help me ç.ç