Comment 5 for bug 893676

According to your error_log, the dbus notifier process dies because of an invalid utf8 string. I wasn't able to reproduce this on my system yet. I'm also not sure how this could have happened, as dbus notifications are off be default.

A simple workaround is to remove all subscriptions: Go to the admin page of the CUPS web interface at

  http://localhost:631/admin

and click on "cancel rss subscription" for all listed subscriptions. You will be asked for your username and password (has to be an admin account).

This is not the real solution to this, of course, but it should stop your theme from disappearing.