Do you have a problem with the CAPTCHA to prove that you are a human when you try to set up Sync? Do you see that image at all? If you can't make out its content (some are hard to decipher) then try to refresh the CAPTCHA image until you get one that doesn't look too hard. Make sure that you do not block (CSRF) cookies. *http://kb.mozillazine.org/Cookies Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes). *Don't click the Reset button on the Safe mode start window or otherwise make changes. *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes