I get the same error, also I get it quite frequently. Here's an excerpt from my .xsession-errors. It starts like this, and then the errors multiply...
(gnome-shell:4706): Clutter-WARNING **: Actor '<unnamed>[<StBin>:0x3ab7010]' should not be mapped if parent '<notification-container>[<StWidget>:0x37a0fd0]'is not visible JS ERROR: !!! Error calling onComplete JS ERROR: !!! message = '"this._notification is null"' JS ERROR: !!! fileName = '"/usr/share/gnome-shell/js/ui/messageTray.js"' JS ERROR: !!! lineNumber = '2249' JS ERROR: !!! stack = '"()@/usr/share/gnome-shell/js/ui/messageTray.js:2249 wrapper()@/usr/share/gjs-1.0/lang.js:204 ("_notificationState",2,wrapper,[object Object],(void 0))@/usr/share/gnome-shell/js/ui/messageTray.js:2075 wrapper("_notificationState",2,wrapper,[object Object],(void 0))@/usr/share/gjs-1.0/lang.js:204 ("_notificationState",2,wrapper,[object Object],(void 0))@/usr/share/gnome-shell/js/ui/tweener.js:109 _callOnFunction((function () {oldHandler.apply(eventScope, oldParams);handler(target);}),"onComplete",[object Object],[object _private_St_Widget],[object Array])@/usr/share/gjs-1.0/tweener/tweener.js:202 _updateTweenByIndex(0)@/usr/share/gjs-1.0/tweener/tweener.js:332 _updateTweens()@/usr/share/gjs-1.0/tweener/tweener.js:344 _onEnterFrame([object Object])@/usr/share/gjs-1.0/tweener/tweener.js:359 _emit("prepare-frame")@/usr/share/gjs-1.0/signals.js:124 (418)@/usr/share/gnome-shell/js/ui/tweener.js:249 wrapper(418)@/usr/share/gjs-1.0/lang.js:204 ([object _private_Clutter_Timeline],418)@/usr/share/gnome-shell/js/ui/tweener.js:224 "' JS ERROR: !!! Exception was: TypeError: this._notification is null JS ERROR: !!! message = '"this._notification is null"' JS ERROR: !!! fileName = '"/usr/share/gnome-shell/js/ui/messageTray.js"' JS ERROR: !!! lineNumber = '2289' JS ERROR: !!! stack = '"()@/usr/share/gnome-shell/js/ui/messageTray.js:2289 wrapper()@/usr/share/gjs-1.0/lang.js:204 ()@/usr/share/gnome-shell/js/ui/messageTray.js:1982 wrapper()@/usr/share/gjs-1.0/lang.js:204 ()@/usr/share/gnome-shell/js/ui/messageTray.js:1937 wrapper()@/usr/share/gjs-1.0/lang.js:204 "' JS ERROR: !!! Exception in callback for signal: showing JS ERROR: !!! message = '"this._notification is null"' JS ERROR: !!! fileName = '"/usr/share/gnome-shell/js/ui/messageTray.js"' JS ERROR: !!! lineNumber = '2289' JS ERROR: !!! stack = '"()@/usr/share/gnome-shell/js/ui/messageTray.js:2289 wrapper()@/usr/share/gjs-1.0/lang.js:204 ()@/usr/share/gnome-shell/js/ui/messageTray.js:1982 wrapper()@/usr/share/gjs-1.0/lang.js:204 ([object Object])@/usr/share/gnome-shell/js/ui/messageTray.js:1507 _emit("showing")@/usr/share/gjs-1.0/signals.js:124 ()@/usr/share/gnome-shell/js/ui/overview.js:632 wrapper()@/usr/share/gjs-1.0/lang.js:204 ()@/usr/share/gnome-shell/js/ui/overview.js:564 wrapper()@/usr/share/gjs-1.0/lang.js:204 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1067265 Title: gnome-shell (3.6) notification bar disappears To manage notifications about this bug go to: https://bugs.launchpad.net/gnome-shell/+bug/1067265/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs