Firefox is a great program but the bookmark saving is terrible. Every time a syste m crash occurs, you will lose your bookmarks and profile regardless of what version you have. The creators are aware of this problem but have not yet been able to find a solution. I simply recomend you save your bookmarks regulary by going to bookmarks>manage bookmarks>file>export. I know this is a pain in the $%# but it is the only way. If this annoys you, I recomend using mozilla instead which is basically a simplified version of firefox.
In the meantime, lets just hope they find a solution soon.
Good luck.
Regards,
Korrupt