As stated in the related question (https://answers.launchpad.net/ubuntu/+question/243724) this seems to be caused by "show live previews in spread" option for the unity plugin.
** Also affects: unity (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of compiz packagers, which is subscribed to compiz in Ubuntu. https://bugs.launchpad.net/bugs/1305438 Title: hot corners stop working time to time To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/compiz/+bug/1305438/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~compiz Post to : compiz@lists.launchpad.net Unsubscribe : https://launchpad.net/~compiz More help : https://help.launchpad.net/ListHelp