Make sure that you do not run Firefox in permanent Private Browsing mode.

• https://support.mozilla.org/kb/Private+Browsing

To see all History and Cookie settings, choose:

• Firefox > Preferences > Privacy, choose the setting Firefox will: Use custom settings for history
• Deselect: [ ] "Always use private browsing mode"

I am not running Firefox is Private Browsing mode. The window that had popped up in previous versions of Firefox when I selected "Clear Recent History" does not appear. My preferences from previous versions of Firefox have not changed upon updating to Firefox 11.0.

Is that menu entry enabled (not grayed out)?

• http://kb.mozillazine.org/Corrupt_localstore.rdf

Try to repair the disk permissions:

• http://thexlab.com/faqs/repairprocess.html
• http://guides.macrumors.com/Repairing_Permissions

Try to remove the Firefox plist file (org.mozilla.firefox.plist).

• http://www.macfixit.com/article.php?story=20060606082246983 How .plist files become corrupt and troubleshooting the results

Go to "~/Library/Preferences" and remove the plist file for Firefox (org.mozilla.firefox.plist)

Create a new profile as a test to check if your current profile is causing the problems.

See "Basic Troubleshooting: Make a new profile":

• https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-make-a-new-profile

There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.

If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

See:

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox