The December image of raspbmc has a vnc server.
If one writes the December image to a SD card and then boot a connected pi it updates itself to the latest level. VNC at this level works in that I get an XBMC desktop and the keyboard and mouse work correctly.
However, XBMC itself fails to actully do anything as any action that requres it to go to the net, fetch add-ons or skins for example gives a blank panel with a single item of "..".
OTOH if I do the initial boot of the pi with it *not* connected to the net I can get in and turn off updating before it has a chance to do anything. Now XBMC works fine, it can see the repos and get add-ons and skins.
The problem in this case is that in the VNC window the mouse does not work. Sometimes I see the pi mouse but it is way to the upper left of where the mouse actually is on the VNC panel.
What I can't figure out is what individual package I need to update to get the working VNC version as if I had let it auto update.
Given I can't find anything on the problem of the updated Gotham system failing is that a WAG would be it has never been been tested on a "clean" install and only works if it was working *before* the update happened.
As I have it working I don't fancy trying an update "to see". :-)