I lost all bookmarks and can no longer bookmark anything

My book marks are gone, I was on the phone with AT&T because my wireless router was not connecting and the Rep told me my computer was slow ( she was remote accessing) and she told me to delete my browsing history as I never had and also cookies. Ever since that my bookmarks are completely gone as well as I can no longer even bookmark any web sites I visit. I did backup my book marks and have repeatedly tried to go through the library window and restore my bookmarks to no avail. Yes I do it correctly by choose file but I receive a message unable to process. I lost so many book marks for not only personal but business as well!! HELP HELP HELP