After filling the above comment found that disabling "Sync to VBlank" might solve the problem. After un-ticking it in CCSM the system refused to switch the user, with the error message. So I went to NVidia X Server Settings and un-ticked same Sync to VBlank here. This helped.
-- Switch User freezes at blank screen https://bugs.launchpad.net/bugs/112518 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
