I have installed UBUNTU 12.04LTS on my desktop. However, during work, the display suddenly becomes black. As the cursor is moved, it starts displaying the normal background as if it is being painted upon using paint brush. Literally, I am able to paint over the black screen fully to get back the normal background and the system works fine for some time before the black screen appears again. If I do not paint also, the normal screen appears back after some time (probably when the screen refreshes after some time, normality returns). I tried changing the screen resolution to a lower resolution however the problem still remains. Need help in resolving this issue including steps (if possible) for getting update of drivers if necessary.