You probably have seen this article, but just in case you haven't, it's a pretty comprehensive list of things to check:

Images or animations do not show | Troubleshooting | Firefox Help

Also, if you are using an ad blocking add-on, you might try disabling that in case it has gone haywire (e.g., bad rule set update).

Thankyou. There was a problem with existing cookies. when i deleted them all sites were able to load properly. I think i have had this problem before after updates of firefox so maybe its something that could be factored into update. ie clearing cookies, cache etc. We all do prefer seamless updates if possible.

For those of us that have trouble remembering our logins, clearing all cookies on every update would be a big headache. But I'm glad it worked for you.