I have two folders on my website that are protected using Apache 2.2.31 basic password authentication. When I access one folder, it displays a dialog requesting my username and password. Once I've entered my credentials, and have no problem accessing the folder contents. When I access the other folder, I immediately get a 401 authentication error. I do not get the dialog requesting the username and password. I have cleared cache and removed the password from the remembered passwords, but the problem persists. I can access both folders using Safari, Chrome, and Internet Explorer. I don't have this problem on my laptop, which is running Windows 10 with Firefox 46.0.1, so the problem appears to be machine specific. My website is hosted on a Linux machine using kernel version 3.12.52. My Firefox 46.0.1 client is running on a Windows Vista machine.