I think this is duplicate or related with bug #118605 and bug #119635 I had similar freezes but, at least in my case, disabling the composite extension completely resolved the problem.
-- 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 the bug contact for Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
