I am also experiencing this issue couple of times every day. Music in background keeps on playing and I can move mouse pointer, but everything else on screen is frozen. Usually if I wait around 30 seconds or if I switch to tty1 and back to tty7 it also usually solves the problem. Also I should note that when I press Ctrl+Alt+1 there is couple of second delay before showing the terminal.
I am using dual monitor setup and integrated Intel graphics chip: #lspci -v | grep VGA 00:02.0 VGA compatible controller: Intel Corporation Xeon E3-1200 v2/3rd Gen Core processor Graphics Controller (rev 09) (prog-if 00 [VGA controller]) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1314871 Title: Ubuntu 14.04 random screen freeze while Normal OS activites To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1314871/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs