Several people have said that when they type in the correct username and password for my site via basic access authentication, they are hit with a 401 authorization error. They are simply copying and pasting in the password, so I'm pretty sure it's not due to incorrect credentials. Considering that it could be the browser settings, I tried the following to try and reproduce the error in IE9:

*Setting the security level to High (this doesn't reproduce the error)
*Setting the user authentication as anonymous (this reproduces the error, but without the login that they see, so it can't be this causing it)

I can't think of anything else that could cause it. Is there an issue with older browsers or some other security setting I haven't tried? Or anything else?

Kind regards,