We're aware of an issue in the game where your screen scroll lock will become stuck. This means moving the mouse to the edge of the screen does nothing, and pressing space bar does not return the screen to your champion.
You can fix the issue by alt-tabbing out of the game client. In our internal tests this clears the issue for the remainder of the game. Changing your options will not fix the bug.
We'll get the real fix out as soon as possible but wanted to get you some visibility on the workaround in the mean time.