Skills and items that target not working properly

During my games when I'm trying to fire skill shots like Ashe's ult arrow or use items like BoRK when I hit the key to use it and click the skill won't go off and I'll end up clicking multiple times before it finally works. I'm not sure if it's my computer that has the problem or what but if I put quick cast on it seems to clear up the problems or the most part but I'd rather not use quick cast for all my abilities. When trying to use my skills the indicator of the ability and ring to show I'm trying to use it will appear but the game will refuse to let me target and enemy or fire the shot.