Binabik: You can export (save) your bookmarks in Firefox (and any browser)

I'm not sure exactly in the old version of firefox since I have 2.0 sitting here right now, but in 2.0, you go to Bookmarks, and choose orginize bookmarks - where then you can find a file, export to export your bookmarks. (Will export to a simple html file.) And then if you lose it again, you can import back in the bookmarks.

I've never lost my bookmarks - I just simple install the 2.0 version and it copied everything over to the new version.