Double-check your proxy settings. If everything seems right, try clearing your cookies and cache:

1. Go to Firefox > History > Clear recent history.
2. Under "Time range to clear", select "Everything".
3. Now, click the arrow next to Details to toggle the Details list active.
4. From the details list, check Cache and Cookies and uncheck everything else.
5. Now click the Clear now button.

Further information can be found in the Clear your cache, history and other personal information in Firefox article.

Still no luck after clearing everything, Verdi. I'm also certain the settings are correct and are verified working with other programs.

Ah - if you've set the proxy in Windows, make sure you tell Firefox to use the system proxy. You can do that in the Network settings.

• Open the options window: Firefox > Options
• Select the Advanced panel and then the Network tab.
• Click the Settings button.
• Make sure "Use System Proxy settings" is selected.

If that still doesn't work, there could be a problem with your profile. The quickest way to get a fresh profile (while saving your bookmarks, history, passwords, cookies and form data) is to use Firefox Reset .

If you don't want to commit to resetting Firefox (it will remove you add-ons and not save your open tabs), you can create a second profile to use for testing this fix with the instructions here - Profile Manager - Create, remove or switch Firefox profiles

How do you set the proxy setting?

Are you entering the IP address and port number in the settings or do you use one of the other to let Firefox detect the setting?

You can try to disable the automatic login prefs and set this pref to false on the about:config page.

• signon.autologin.proxy -> false
• network.automatic-ntlm-auth.allow-proxies -> false
• network.auth.use-sspi -> false
• network.proxy.share_proxy_settings -> false

• http://kb.mozillazine.org/about:config

Verdi, the proxy isn't set through Windows. The other programs are using it successfully are using it through their own settings as well. Creating a new profile did not solve the issue either.

cor-el, yes, I'm setting the address and the port provided by my VPN service specifically for Socks5. I've already disabled those configs after Googling this issue before making the thread. They did not help.

Have you seen this post:

https://support.mozilla.org/en-US/questions/926378

It seems that with some proxy services/protocols, you may need to change the following preferences in about:config

• network.automatic-ntlm-auth.allow-proxies
• network.negotiate-auth.allow-proxies

This extension may also help: https://addons.mozilla.org/en-US/firefox/addon/proxy-authentication/

Yes Cww, I have already tried that to no avail.

Does it work if you go to the proxy login page and use http://username@xxxx.com or the IP variant http://username@xxx.xxx.xxx.xxx

This is a really nice try, but after changing these settings in about:config and restarting I still get the prompts of the type:

The proxy moz-proxy://XXX is requesting a username and password. The site says: "moz-proxy://xxx".

...that will repeat infinitely until I hit cancel.

I have tried a few other about:config changes but nothing has yet worked.