Comment 70 for bug 138691

Someone else mentioned the realtime kernel.

I never had any problems like this UNTIL I installed the ubuntu-studio audio apps package - which includes the realtime kernel. Now I get the same networkmanager/message bus problems reported here and fauilure to shutdown (most of the time - sometimes it works, sometimes it doesn't)

Is there any easy way to switch back to the normal kernel to test if that will make the problem go away?