This happens every day, seemingly randomly.  I constantly have to write the email, highlight it all, and set the desired font and font size. This happens despite the fact that I (more than once) have gone into Options and set a default.

Also, sometimes the email will appear to be fine, so I send it. Then, I will see it after it's been sent, and there are 2 different fonts in it. This is driving me crazy, can someone please advise?

More info- I am using this on Firefox 20.0.1 

-when I go into settings, the screen where you put in your desired font, and signature - the drop-down box for font name won't even let me select a font. The font size drop-down will, but not the font name.