I downloaded and clicked the dmg to install latest update. It got to 51% complete and then stopped instructing me to close Safari. Sarfari was already closed and not running. Hit retry and got same message. Tried a reboot and install but still got same message. Don't understand why it says close when it is already closed?
It's probably still running somewhere in the background. If you are on a Mac, use the Activity Monitor to close running applications. On Windows use the Task Manager.