I have just had latest update install for mozilla firefox. Now my screen is breaking up into black rectangles and is not rendering properly. I had this problem but last update seem to fix it. I can't tell you how utterlydepressing this is. I don't have any knowledge to fix it and if it goes back to how it was permanently then, much as I love firefox I'm dumping it. Unless there is a solution. It would be nice to roll back the update and also choose not to install any in future. god's teeth I'm on windows 10 if that makes a difference.