Comment 29 for bug 664763

okay so from what I've learned so far is

cannot register existing type `_PolkitError'

might be because your on a 64 bit platform?

Can you try running the live cd of 32 and 64 and see if you can recreate the problem?

also was this a fresh install or an upgrade? and how did you do this upgrade if it was

and I doubt this will work but try to kill the nm-applet and restart it using sudo and you can also try gksudo