My new Mac Pro will not shut down on it's own anymore. When I select shutdown, the little twirling icon just keeps twirling and will not turn the computer off. 1. I install some software on the computer and am guessing that is what it causing the problem, However I don't want to reinstall the operating system if there is a fix. 2. Current I have to hold the power button down for a force shutdown. Is there some system utilities out there that I can run on the computer that will fix whatever is causing it to get hung up and not shutdown? Any help would be great??