I built dbus with the python USE flag so that I could use ROX-Session but ROX-Session would not start. I discovered that dbus requires the libxml2 python bindings and these had not been installed because libxml2 had not been emerged with the python USE flag. A USE flag check is needed. However, I gather that the dbus bindings have been split from the main package starting from version 0.9 so you might want to check that out first.
0.62-r1 should use expat from now on so it shouldn't be an issue. retest and reopen as needed.