OS is Windows XP 64-bit SP2. Upgrade from version 3.6.28 to version 12.0 doesn't work properly because I lost bookmark functionality. Bookmark menu is there, but no bookmark entries. - I tried to add a bookmark (visit a page, then 'bookmark this page'), but that doesn't work: no error message, but nothing is bookmarked - I tried to restore bookmarks from previous Firefox (yes i previously made backup), but that doesn't work either. I tried that in 2 ways: 1) Show all bookmarks -> Import and Backup -> Restore -> Choose file -> bookmarks-2012-05-06.json; I get error message 'Unable to process the backup file'. 2) Import and Backup -> Import bookmarks from HTML -> bookmarks.html; I get no error message, but nothing is imported. - I tried to rename places.sqlite to places.sqlite.old and start Firefox. Didn't help. - I tried to uninstall Firefox and make clean installation (didn't keep old settings), but that didn't help either. Bookmarks don't work. - In the past year I tried to upgrade Firefox 3.6.xx to previous versions (i think they were 4.x, 9.x, 10.x), but I ran into the same problem, so I reverted to 3.6.xx. Problem this time is that 3.6 is no longer supported, so upgrade is not optional. Thanks in advance for your help.