but have you deactivated any new plugins you may have added before this happened?
do you have debug mode on and is there an error?
does an error show in the firefox console?
https://developer.mozilla.org/en-US/docs/Tools/Web_Console
then open up the page you have the issue with, make sure you are on the console tab and tell us if it shows any errors.
thanks
Can you pm me your admin access details, I'll take a look at the issue?