MacBook Pro mid-2010 10.8.5 running Firefox (39.0) and won't display content in boxes

A number of sites (Outlook, Google Maps, New York Times) won't display properly. When there's a white box with text in it, it stays blank. Just shows a white box overlaying the other content. An example would be in Google Maps. If you look up an address, the map will show but the boxes upper left and lower right that give you prompts (the + or - boxes or the satellite vs hybrid etc) are all just blank white. In some cases this happens when reading a story online where you can load comments (i.e. NYT) and the comments box clearly loads but stays empty. Really frustrating. Any suggestions?