Kathy, do you use Vista? I thought the same as Karsten, but I wasn't sure that you had installed any add-ons, so it must have been fairly standard. I searched on that error because it sounded odd and someone said running as admin worked for him. Try this:
Right-click the Firefox icon on the desktop and select 'run as administrator'.
If it works, try closing Firefox and then re-open as you normally would.
