cant even get to the loading screen?

so basically i tried playing league today it was ranked flex. and everything was fine as usual but after we picked our champs and it had to show up the loading screen. black screen appeared and u cant do shit after that not even ctrl+alt+delete nothing works i had to unplug the my computer to turn it of. but i know its not an internet problem because when i unplugged the computer i connected with a different one and it did connect so wtf is going on. rito help!. and by the was it was working fine 12 hours earlier