Comment 6 for bug 1248211

This affects me too in exactly the same way.

Based on my digging, there are more than a few people experiencing this particular combination of issues after the 13.10 upgrade (NM issues, User Account management "unlock" is greyed out, drive mounting/unmounting issues, shutdown/reboot issues).

I've seen it suggested this may actually be a policykit issue, since these are all things that require elevated permissions and only occurs in the GUI. This particular system I'm on may have been upgraded more than once, but I'm not sure since I don't recall whether I did a clean install of 13.04 or upgraded from 12.10 (and more). So, it may be something that doesn't present unless you've gone through multiple chained upgrades.