I am using ubuntu 12.04 and everything was working fine but suddenly the top panel and side bar (launcher) has stop responding to mouse or my touch pad. I can bring the dashboard using keyboard shortcut but can't type anything or click on anything. Same problem is with top panel. For eg. I can't click and open the menu on the top right corner to logout or shutdown, for that I have to press power button on my laptop or Press Alt + F4 to do the task. I tried to find this problem online but didn't found one anywhere? Please help me to solve this problem. Thank you in advance.