I was able to get the networkmanager docklet to work by downgrading to NetworkManager 0.8-r1 (I'm on Gentoo Linux, so that may be a Gentoo-specific release, I'm not sure). All versions/revisions of NetworkManager 0.8.1, 0.8.2, and 0.8.4 I had at my disposal worked with the docklet.
I was able to get the networkmanager docklet to work by downgrading to NetworkManager 0.8-r1 (I'm on Gentoo Linux, so that may be a Gentoo-specific release, I'm not sure). All versions/revisions of NetworkManager 0.8.1, 0.8.2, and 0.8.4 I had at my disposal worked with the docklet.