For something like this, clearing your cookies and cache should work.

1. Open the Tools menu, then select Clear Recent History... .
2. In the Time Range to clear: drop-down, select Everything.
3. Click the arrow next to Details to display the list of items that can be cleared.
4. Select both Cookies and Cache.
5. Click Clear Now .

But I also noticed that you have the add-on "XUL Cache", which is a result of malware being installed on your system. See http://www.bleepingcomputer.com/forums/lofiversion/index.php/t192538.html

I was having the same issue for a few weeks. But just checked the FireFox error console and found a problem on regular facebook home page ( Without HTTPS ).

Error: uncaught exception: Error: Permission denied for <https://www.facebook.com> to get property Proxy.InstallTrigger

Then I used HTTPS for facebook the the problem is gone :)

The problem is due to security permissions for regular HTTP pages.

To solve this blank page issue just do the following :

1. Visit : Security Settings on Facebook

[https://www.facebook.com/settings?tab=security]

2. Enable Secure Browsing.

And you are done :)