I'm trying to do customer support for a web application that we develop and host. A client just sent me screenshots of "our application" putting up a standard Windows username/password box, then failing to authenticate. The logs, and everything else I know about our system, indicate that it wasn't actually our application that asked her to authenticate. The "authentication_failed" message looks like this, in MS IE6:
I did some Googling on the issue, and the word seems to be that it's a proxy server that gives this message, but none of the first dozen or so results told me conclusively what proxy server product it was. My questions are: is it a specific proxy server product and can you tell me what it is? I need some more specifics before I go back to the client. Thanks in advance.