In-Game Bugs???

Many of these things have been occurring while I've been playing norms and ranked. Sometimes my cursor in-game would get stuck in a small area, causing me to move my mouse until it returned to its normal DPI, and this has happened many times. Also, my screen has turned black, causing my mouse to not even work on the monitor that turned black, forcing me to restart my computer, since using task manager doesn't work. This happened TWICE in my ranked games, which made me lose my games. So thanks