I confirm the problem. XUbuntu 13.04, kernel 3.8.0-25-generic. I think this is a problem with X-server.
** Package changed: ubuntu => xorg-server (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1184451 Title: Ubuntu 13.10 random screen freeze while Normal OS activites To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/1184451/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs