[ubuntu] Desktop screen and mouse cursor flashes

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http://ubuntuforums.org – Friends,I have a Dell Vostro 3550 laptop which cam preinstalled with Ubuntu 10.10 and has the following configuration:CPU: Core i5 2nd Gen GPU: ATI Radeon 6630 at the time it first shipped the desktop screen and mouse flickered and there were no desktop effects and I didn't like it, so I did a clean install of Ubuntu 11.04. With 11.04 though the desktop effects came but the Desktop screen and the mouse cursor has severe flickering problem. Every time the flickering happens after I have right clicked on something the "context menu" disappears. Consider this that in Firefox when I rig (Hardware)