Binabik: Have a look at Mozillazine Knowledge Base: Lost bookmarks , it may give you some help also on how to find them. According to this if it is caused by the installer not properly detecting all Firefox processes, they are not lost.
(peida) Kui Sa tahad kedagi tema emakeeles tervitada, vaata meie Mängija Sõnastikku "veel keeltest" lingil lippude all. (pauloaguia) (näita kõiki vihjeid)