Just started happening. When I go to compose an email in gmail all of the functionality works (Insert from drive, insert photo, insert emoticon, etc...) but when I click the insert attachment button nothing happens. I've already tried the following 1- Restarted in safe mode 2. Cleared Cache 3. Reset Firefox 4. Went into about:config and changed the network.http.spdy.enabled to false Still having the same problem and can't add attachements. This is obviously a deal breaker for me and using Firefox so any help would be greatly appreciated. Thanks!