Comment 9 for bug 216908

I have exactly the same problem, and have been looking everywhere for some light to no avail.
What's "funny" is that my machine is a desktop, with wired LAN. So I guess nothing to do with WiFi...
I am on fully updated Hardy Heron updated from Gutsy.
While some people seem to experience also a complete hang-up of the machine (never shuts down after showing the same blurb on the screen), mine does shut down as described in subject of this bug.
Very similar (well... identical except fo rthe "hang-up") to bug #138691 (https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/138691)