Here's a list of things that I've found I can no longer do with the latest version of Firefox (36.0.4) but which I could do fine on the previous one. Not sure how to fix this, short of waiting for the next update, which I hope will be soon.
Things I don't seem to be able to do include...
- view my Wordpress.com sites' stats pages - they all show up as a blank grey page (fine on Safari)
- use FlightRadar.com - no aircraft appear and although I can zoom in or out I can't use the grab and move tool to move the map (fine on Safari)
- use Storify properly - it stops at the end of the first page and the 'read next page' link doesn't click to go anywhere (infinite scrolling works fine on Safari so I never see this button, it worked fine on the previous version of Firefox too)