This article explains a workaround for Firefox version 30 on Mac OSX when a user is not prompted for authentication, but instead receives a 401 Unauthorized Access error.
- Launch FireFox.
- Type about:config into the address box, then click the button saying I'll be careful, I promise.
- In the search box type ntlm, the screen auto-filters to some properties.
- Locate the line "network.negotiate-auth.allow-insecure-ntlm-v1", then double-click it to change the value from false to true.
- Open a new browser tab within FireFox, then browse to the site. You should now be prompted for credentials.