When I boot my mac, it works fine for 20-30 minutes. The Wifi works. Chrome and other browsers work. 30 min in to use, issues arise. 1st, both Dropbox and Crashplan menu bar icons freeze (when hovering over it shows the busy cursor) 2nd, Chrome and other browsers freeze and are unable to work after force quit and restarting. 3rd, Wifi stops working; any attempt to resuscitate wifi by turning it off/on through the menubar icon does not work. In fact, when I turn it off through the menu bar icon, the icon stops reflecting the status of on/off. Every time this happens I have to to do a hard reboot of my Mac. If I use the option to shutdown my mac from the main menu, it will go into shutdown mode but never actually "shuts down" instead a grey screen stays on the screen. What is wrong with my mac???? Note: I accidentally started downloading mackeeper but canceled it before it could finish. I then deleted the file.