I have installed ubuntu 12.04 through update manager, I had 11.04 as the previous version and everything goes fine from downloading the packages to restarting the system.

After restarting I found that there is no graphics related items in the installation and I cant able to move my trackpad in laptop. It shows a black screen with the desktop items but cant able to edit any items.

There is no menu items available in the desktop. Can any one help me in this.