Firefox is not displaying an authentication prompt when using NTLM/IWA authentication
You are using NTLM/IWA authentication and Firefox 1.5 and are not receiving an authentication prompt
Firefox 1.5 and newer can be configured to use Single Sign-on (transparent authentication). When Firefox is configured for NTLM/IWA authentication, it will automatically send the client credentials to the ProxySG when it receives an authentication request. The result is the client never receives an authentication dialog box. If you want to disable automatic and silent authentication so the user is prompted for their credentials, then please do the following:
The authentication dialog box should now show up on that browser.