Map Moving w/ All Mouse Movement

About 20% of the time when I load into a game, the map drags with my mouse. It used to be only when I click-and-dragged (making dragging items and champions impossible), but now today for the first time it started doing it on all mouse movement, even when I wasn't clicking, making the game impossible to play. Please advise as to how I can fix this? Reloading the game does not work and only surrendering and going into a new game fixes it.