Is your Bookmarks menu or Bookmarks sidebar completely blank? Or does it have a few pre-installed bookmarks?

First, you may want to make a backup of the Firefox profile folders on your PC. They contain not only your current bookmark list, but folders of backups. But these are not saved forever. To back up Firefox, see Backing up your information.

The following article has suggestions for recovering bookmarks: Lost Bookmarks | Troubleshooting | Firefox Help.

This also might be useful: Recovering important data from an old profile.

Any luck?

This really sucks. I lost my favorites with 4.01 too. I'm going back to Explorer. You really let me down with this mess.

Did you try this?

I just downloaded Firefox 4, and I also had the same problem...my IE favorites folder didn't get transferred.

I found this mozilla link: http://support.mozilla.com/en-US/questions/818060?s=just+downloaded+Firefox+and+can%27t+find+my+favorites&as=s#question-reply

... and I was able to successfully import my files. Not sure if it was because I hadn't deleted IE9 from my computer. When I opened IE9, I could access my Favorites, but they weren't accessible from the Firefox browser...until after I imported them.

myself was a FF user for last 12 yrs !! even i remember recommending ppl abt it...but FF 4 is a real PAIN IN THE APPROPRIATE PLACE....

it hogs memory...for simple functions (available by default in previous vers) ,now u have to install add-ons for them (like new tab button, FF4 either lets u have a new tab button OR the "+" button near opened tabs..but U CANT HAVE THEM BOTH SAME TIME!! WHAT THE.......

PC hangs/freezes almost everytime i ran FF 4 ..and for that i have lost valuable data..mind u, my machine config is not outdated. I have reverted back to previous vers FF 3.6...and am NOT UPDATING IT SOON....

ALL OF U FOLKS HAVIN PROBS WITH FF4 : easiest solution for all your probs -

1) get rid of FF4 and install the previous vers - http://www.mozilla.com/en-US/firefox/all-older.html after backing up - https://support.mozilla.com/en-US/kb/Backing+up+your+information

OR

2) get an alternative browser

yes folks, the above solution will at least give u peace of mind and a more peaceful good night sleep