Is that uploading done via a regular Browse button like you see on this forum to add an attachment or is it done otherwise e.g. via a plugin like Flash or Java? Did ATT support manage to do this with the current Firefox release? ---- You can try to create a new profile as a test to check if your current profile is causing the problems. See "Creating a profile": *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files. *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox You can also try to reset Firefox: *https://support.mozilla.org/kb/Basic+Troubleshooting Also make sure that your security software (firewall, anti-virus) isn't blocking uploads.