Launcher will not let me log in, will exit it, and no known fix.

Hello. Earlier today, I wanted to play some league, and when I opened the launcher, it was running a bit slow, which was a bit odd, being as I have exceptional internet access and a decent computer. When it finally loaded and I hit [PLAY], it took me to the log in animation, but instead of epic music playing and a cool animation, all I saw was a black screen with no sound, but everything else seemed fine. Weird, huh? It didn't stop there. As soon as I clicked to sign in my password, the whole launcher looks like it was highlighted, but instead of blue it was white. It also moved up and to the left a bit. I was very confused, and a second or two later, a window popped up saying that the lol client has stopped working, and it asked whether to wait for it or just close it completely. I tried, tried, and tried again to no avail. I resorted to re-installing it, and guess what? It didn't fix it :( I was just wondering if this is a known bug/error and if there is a fix. I never heard of this bug before, and even after googling for a while, nothing remotely similar was shown. It's very peculiar why this is happening when my whole computer is fine, and other big games/programs are running fine. Again, I would greatly appreciate any help. Thank you for taking the time to read this, and have a good day!

P.S. I would like to point out one time during my "quest" in trying to fix this issue, I even tried to let it load up to the username/password screen, and waited 5-10 minutes, and then it let me put in my password, and very slowly let me log in. When I got logged in, it was just as bad. The whole launcher was laggy, and when I attempted to look at my profile, it crashed again. It immediately went back to what it has been doing after that.