Frank_Rizzo - 8:02 pm on Jun 19, 2010 (gmt 0)
Could it be FF importing your IE bookmarks?
Everytime you install a new copy it could be accessing IE / some other browser bookmarks in order to populate FF bookmarks as default.
Did you once install an FF add-on for managing bookmarks? It could be something still in there trying to store bookmarks but it has had the rug pulled from underneath it.