Comment 31 for bug 540950

Ah-ha! I did not have python-wnck installed, and without it I was getting the exact same error as the OP. Installing python-wnck solved the problem. So I'm not experiencing this same bug in Debian. Maybe it is Ubuntu-specific. My situation was related to bug # 540950 which I filed, in that python-gnome2-desktop no longer exists in Debian sid, and instead other packages are required for Dockbarx to work: probably python-wnck and python-gnomeapplet, as you suggested.