said by Grail Knight:I had this problem briefly and found an extension was causing the issue. It was an older extension to auto-close bookmark folders. Removing it solved the issue.
If you start Fx in Safe Mode and the bookmarks feature is working chances are an extension is to blame for the issue you are seeing.
Thanks for the tip GK. I have the add-on Bookmark Duplicate Detector and I just noticed the note on the add-ons website that it's "Not available for Firefox 13.0". Will uninstall it and see if that solves the issue and if not will follow your suggestion.