What happens when you try to bookmark pages: just nothing? Does it matter whether you use Ctrl+d, or click the star icon in the URL area, or use the menu?

There was a thread yesterday that might be similar to your issue: I can't add new bookmarks all of a sudden. Still occurs in safe mode.

Problems with bookmarks and history not working properly can be caused by a corrupted places.sqlite database file.

You can check for problems with the places.sqlite database file in the Firefox Profile Folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file