I just downloaded Ubuntu 12.04 today, this is my first time with Linux. Everything is up to date. However there seems to be stability issues. Nothing has crashed (although I've only been using it for a few hours), but icons on the dashboard disappear, when I search for something using alt F2, my result may or may not come up and even if it does and I click on it, nothing happens. From time to time portions of the screen will become pixilated as if the whole system were about to crash. Does anyone have any idea what I can do to help these problems? Thanks!