Comment 25 for bug 638217

sorry for posting this comment twice, i accidentially posted it in the duplicated version of the bug ....sorry for that
I have the same problem here (but no 64-system), and I found a workaround (if one of the above solutions works for you, just ignore this one):
You have to start the System-Administration-Terminal, that gives you root privilegs.
now you can run gnome-activity-journal.
This should work. But zeitgeist, which is, i guess the reason you need activity journal for, depends on executing user.
So i tried a bit, and found a trick.
For example, if you want to set a blacklist, set the blacklist in the with root rights started activity journal, then close it.
now run nautilus with root, open /root/.locale/zeitgeist/ and copy the blacklist.prickle file to /home/your_name/.locale/zeitgeist/
now set the file ownage and the rights to your username (easy with nautilus, rightclick properties...you know how to)
you can now close all terminals, i dont know if zeitgeist has to be restarted, i just rebooted and if you now open a file, you have blacklisted with the trick, it will not be shown in the recently used documents.
hope it works with you!