If the mouse cursor still moves then Xorg is still working. This usually means it's the gnome-shell process that has frozen or crashed, so please follow these steps:
1. Look in /var/crash for crash files and if found run: ubuntu-bug YOURFILE.crash Then tell us the ID of the newly-created bug. 2. If step 1 failed then look at https://errors.ubuntu.com/user/ID where ID is the content of file /var/lib/whoopsie/whoopsie-id on the machine. Do you find any links to recent problems on that page? If so then please send the links to us. 3. If step 2 also failed then apply the workaround from bug 994921, reboot, reproduce the crash, and retry step 1. Please take care to avoid attaching .crash files to bugs as we are unable to process them as file attachments. It would also be a security risk for yourself. ** Package changed: xorg (Ubuntu) => gnome-shell (Ubuntu) ** Changed in: gnome-shell (Ubuntu) Status: New => Incomplete ** Summary changed: - Xorg freeze + Screen freeze -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1933118 Title: Screen freeze To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1933118/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp