Ok If you are on Win 7 , even after you uninstalled Firefox there are 3 folders in which you have to find and delete still on your hard drive to fully remove firefox. Yes this is a major pain in the keister.

First Back up your bookmarks , Go to bookmarks>> Organize Bookmarks (window opens of bookmark manager) Select >>Import and Backup Next Select Export HTML (as you see there is Import HTML) this you will need when reloading Firefox) Save your Bookmark.html to Somewhere like your desktop.

Next UNISTALL Firefox

Next go to start (windows bottom left) click it, on right hand side select computer, which bring open window with drive directories, select the C: drive. Once open Do a File Search for Mozilla.

Delete these folders (Just the folders with name Mozilla)

C:\Users\*username*\AppData\Roaming\Mozilla\

C:\Program Files\Mozilla Firefox

C:\Users\*username*\AppData\Local\Mozilla\Firefox

I Actually had to do this for a friend remotely. after the 2nd unistall I was urked so to say. (Mad) till I found it don't remove all your files off on a unistall.

I hope that helps :)

IMO, try deleting the places.sqlite file in your Profile folder when Firefox is closed. When you start Firefox, a new places.sqlite file will be created using one of your bookmark backup files which are saved automatically when you close Firefox (ten backups are stored).
https://support.mozilla.com/en-US/kb/Profiles#w_how-do-i-find-my-profile

Hopefully, that will solve your problem without having to un-install or delete everything, and start all over again. If it doesn't fix the problem with not being able to save new bookmarks, let us know and we can probably come with something else short of a complete re-install.

BTW, with a problem like this, I sure wouldn't trust a file created by exporting in HTML format as having all your bookmarks.

See:

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox