Since the advent of Firefox 3, a small but diminishing number of users have reported that Bookdog and/or Firefox were unable to read their bookmarks. With Bookdog, the error often shows up in a dialog reporting "sql error 1: Unsupported File Format". We've developed a tool which has solved the problem for many of these users.
To try the tool, download Firefox-Fixxer, unzip it if necessary, run it and click through the dialogs.
If this doesn't work, the next step would be to send us your data.