i'm experiencing the same problem (on natty) with this version of network manager. i upgraded to it (from the gnome 3 ricotz testing ppa) in order to have better gnome shell integration.
an obvious solution would be to downgrade to the stock network-manager version, but i'd like to try something else first. does anybody know of a way to make ubuntu one recognize this nm-version?
the problem seems to be similar to when the dependence on nm was hardcoded into u1 and u1 didn't recognize any network connection when nm wasn't used. but that was fixed a while ago and this time the problem is not that nm isn't installed.
in my opinion, the problem can have two causes: either ubuntu one doesn't recognize the nm-version, or nm doesn't manage to make the connection "public" to other services such as u1. but i think it must be the first one because evolution or liferea or other internet services dont seem to have any problem with the network detection.
sorry that this isn't an actual answer, but it's an attempt to define the problem more concretely.
edit: i just saw another askubuntu post on the same topic that had a workaround that seems to work: Network Manager 0.8.999 and Ubuntu One