I just played with my friend and we were on Summit playing Firefight.
Every time when I was on B site and in the room that's the nearest to the Terrorist I got some kind of strange mouse bug. I made a video of it.

Not every single time, but mostly, when I right clicked it I lost control of the game itself and the mouse pointer from the Main Menu was showing when I tried to look around in game (sadly, I don't know why the Main Menu mouse isn't visible in the video even though I saw it in game). And at another round you can see the mouse but this time from windows.
This was the very first time I experience a bug like this and only in this match in that exact room. Later on other Maps etc. it didn't happen again.

Youtube Video