When I've got windows open on two monitors, when trying to pick the window on my second monitor (and sometimes on my primary monitor), there is a bing (noise to say I'm doing an illegal action) and it doesn't allow me to do it. This has only started since the last update and is not consistent. The way round I've found for it is to go the Window menu and pick the file on my second monitor and then it's all back to normal again.