I am also encountering this bug. For me it seems to be triggered by use of volume keys on keyboard, which correlates with what is discussed in this thread: http://forums.fedoraforum.org/showthread.php?t=230568
A temporary workaround on fedora was to disable the media keys functionality of gnome. So I'm thinking this is an issue with gnome more so than ubuntu itself.
I am also encountering this bug. For me it seems to be triggered by use of volume keys on keyboard, which correlates with what is discussed in this thread: forums. fedoraforum. org/showthread. php?t=230568
http://
A temporary workaround on fedora was to disable the media keys functionality of gnome. So I'm thinking this is an issue with gnome more so than ubuntu itself.