This has been going on for about 4 weeks now. I just upgraded to version 41.0. Neither upgrading, nor refreshing, nor starting with addons disabled has fixed this problem.

I noticed that certain things in Gmail were not displaying correctly. Some icons were missing and in some cases things were smooshed together and there was extraneous text overlapping other things. I compared this to what I saw in Opera which was displaying correctly and there was clearly a problem. There still is a problem after taking the above mentioned steps. If try composing an email, all the icons in the bottom two rows for formatting and other options do not display. In calendar a version of the same things happens. In Drive it is also a problem but it also looks like the text is much lighter than in Opera for the same things like document titles in the document list. And then when trying to go in an open a document or create a new one I can't even do that in Firefox. What is going on? Has google changed how it displays things and something needs to be fixed in Firefox to catch up? At this point google apps are unusable in Firefox.