When I start Firefox without an internet connection, the existing filters are not shown (only the "add filter" button is shown), this I understand. But when I then connect to the internet, even after refreshing toolbar data, the filters are still not shown. I have to disable this functionality in the settings and then re-enable it to see them.
Please refer to: http://groups.diigo.com/group/Diigo_HQ/content/filter-not-showing-2763767