Hi I installed yosemite a few days ago, and now when I try to shutdown/restart/force quit nothing happens. Also, my volume buttons don't work, my power button doesn't work and my brightness buttons don't work. I tried restarting from the command line but that doesn't work either. I went to my activity window and it said "loginwindow not responding". I tried force quitting but that doesn't work. Any other ideas? Is this a common problem with yosemite?