This happens to my family all the time. I have been trying to help them and maybe you can test something for me. When it tells you its using the camera, log in to another user and see if you can use it there. I am wondering whether this software issue is worse than just an app not releasing it for one user and if everyone is affected.
Closing the lens, unplugging it and plugging it back in seems to let them use it again by the way.