(Note: These directions are for the most recent version, older versions should be almost the same after you get into the options menu)
1. First, open Options: (Found in the Menu at the top right of your browser)
2. Go to the Privacy Tab
3. Under History make sure that (temporarily at least) “Remember History” is selected:
4. Click the link that says “clear your recent history”:
5. Select a Time Range to clear: (Everything or Today is recommended)
6. Be sure that the first 5 boxes are checked, then click “Clear Now”:
7. Change History setting back to what it was originally: (Optional)
8. Click Ok, Close Firefox, Re-open and try again.