Your Firefox settings and info are kept in a folder separate from the Firefox program, called your profile folder. Try creating a test profile, to see if the problem still occurs. See Profile Manager - Create, remove or switch Firefox profiles

thanks for the reply but I don't know how to get into the folder...thanks.

To fix computer freezes or facebook freezes problem, follow these guidelines to fix it:

• First, small size of RAM makes computer slow.
• Secondly, corrupt windows registry causes freezing in computer.
• The third most important thing that you can do to optimize your Facebook is to optimize your internet connection.
• So it is recommended you use a system utilities software that provides the feature of internet optimizer.
• Also remove unwanted add-ons/extensions from your browser.
• It is also recommended to clean system junk and browsers junk.

The above guidelines allow you to Avoid Facebook Freezing and keep your Windows properly maintained.

I got some help from this article to avoid Facebook Freezes.

Hope it works for you also.