I have upgraded to OSX Yosemite and done all the software updates. No matter my attempts to remove a REPEATING WINDOW, it will not disappear. I have restarted and shutdown the computer several times. The window is: "Are you sure you want to shut down your computer now?" (and the rest of the options for the power). My computer is 2008 MAC PRO. It is running on a direct Ethernet connection. I have not attempted to reinstall the operating system, nor do I want to.