Comment 5 for bug 638217

Here goes my theory:

Zeitgeist was running (because you had used GNOME Activity Journal, Sezen, Unity, an application with Zeitgeist integration or whatever) at the point you installed the GNOME Activity Journal update.

The latest GNOME Activity Journal includes (and requires) an extension for Zeitgeist which provides the GetHistogramData method. However, since Zeitgeist was already running (and extensions are only loaded when Zeitgeist starts) it wasn't being used yet when you tried to launch the Activity Journal.

After restarting Zeitgeist (manually / closing your session / rebooting the computer / whatever) the extension gets picked up the next time Zeitgeist starts and so this problem shouldn't be happening again.

Can you (and the people from the duplicates) please confirm if I am correct?