Recently I faced a problem with Firefox (My favorite browser).
My bookmarks tool bar became blank after I downloaded certain addons.
After a long time I was looking at the addons for firefox and it was great.
I downloaded a few of them, but than when I restarted my firefox the bookmarks toolbar had a problem. All the buttons on it disappeared.
I had a look in the Bookmarks menu > Bookmarks Toolbar Folder and everything was there, so I was certain that there was problem with my bookmarks toolbar.
I have thinking about it I tried something to solve this problem out.
And here is what work for me:
Click on start (only for windows users)
than search for firefox (for vista users)
than select Mozilla Firefox (Safe Mode) (if you use some other operating system than you need to find out this safe mode option your self, but its easy.)
Than a small menu will open with few options. (remember first shutdown firefox and than perform this steps, or else it wont work and shutdown means close all the firefox windows)
In that menu select the option that says reset all the toolbars and save and continue.
And than (dance!) problems solved.