I have used Firefox for many years. However, since installing Firefox 4 it has lost bookmarks on too many occasions. It is not a trivial matter, unfortunately, because these bookmarks actually represent work opportunities for myself. I have persevered with Firefox 4 (I really have!) because I like it and I was loyal to it. But it has happened on too many occasions now. I will now use Chrome and I have uninstalled Firefox 4 from my computer. I hope you can sort out the problems soon.