bug : cant use q spell and b for back with Katarina

It happened during several games when i played katarina (and only with katarina)... During the game for no reasons, suddenly i cant use q spell and b for back. I cant use the spell even if i try to click directly on it. I restarted completely the game (i disconnected the game and close league of legends) then i returned in the game but this changed nothing. I tryed to change my control so i used "w" instead of "q", "e" instead of "w" etc. but the problem depends on the spells and not the keyboard, so i couldnt yet use the spell (Bouncing Blades)... In the forum at the end of the game, someone said it happened to him in an other game (i supposed he played katarina like into this game), he couldnt use q, b and r... he restarted... I personnally didnt tryed to use "r" since ennemy must be close... Since few weeks, I reinstalled the game but this happened again.