In my case the deinstallation of ulatencyd has solved the problem. I had the problem in the old install, made a clean install and at some point started seeing the problem again. Somehow I guessed I should try deinstalling ulatencyd and it helped indeed. Installing it again and rebooting makes the problem appear again.
I have reported the issue to ulatencyd as https://bugs.launchpad.net/ubuntu/+source/ulatencyd/+bug/1404653 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1240336 Title: Not authorized to perform operation / Unable to determine the session we are in: No session for pid To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdm/+bug/1240336/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
