Clear the cache and the cookies from sites that cause problems.

"Clear the Cache":

   Tools > Options > Advanced > Network > Cached Web Content: "Clear Now" 

"Remove Cookies" from sites causing problems:

   Tools > Options > Privacy > Cookies: "Show Cookies" 

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

   Do not click the Reset button on the Safe mode start window or otherwise make changes. 

   https://support.mozilla.org/kb/Safe+Mode 

Also, try updating your firefox to the latest release

   Help > About Firefox 

   https://support.mozilla.org/kb/update-firefox-latest-version

User follow up:
https://www.facebook.com/Firefox/posts/10201458948508452

I am suggesting a new thread to be create due to a lack of response and since we're now on version 23.0.1.

Thanks!