Are you experiencing the “League Of Legends Fix Visual “Hover Over” Blue/Red Block/Box Bug”? There are two causes that I know that will make you experience this.
1.) Go into NVIDIA control panel – 3D settings – Adjust settings with preview
Make sure to use the “3D application decide”. If you use the other settings you will have issues with the League of Legends Fix Visual hover over box bug.
2.) Go to the League of Legends folder. Then click on “Config” folder. There is a game.cfg file and edit it in Notepad. Make sure the colors is set to: “32”. ATI users will experience this bug more than Nvidia users.