On certain systems, a bad interaction between Unity, the GL driver and the kernel may cause the system to hang.
As There are three session types available which are :
“Unity” which requires 3D driver support.
“Ubuntu Classic” which runs GNOME with gnome-panel. It supports all video hardware and video drivers.
“Ubuntu Classic (No Effects)” which runs GNOME with gnome-panel. It is in 2D mode only.
So we can select either Ubuntu classic or Ubuntu Classic (No Effects) to overcome the issue.
To switch to above 2 option
select Ubuntu Classic or Ubuntu Classic(No Effects) from the menu to choose the session which is located in the botoom panel while login.
Click on the power button in the upper right corner after login and choose the last option, System Settings.
Search for Login Screen
Double-click to display
Choose Unlock and enter your password
Select Ubuntu Classic as default session.