Something that has always bothered with MOSS and Vista is the fact that I have to always log on when I open documents from the SharePoint interface. I was not sure if this was a Vista thing, a SharePoint thing, or a combination of the two that was causing this behavior. It always just seemed to happen. I would even get complaints from coworkers and clients about this behavior but couldn’t never fully determine why this was happening.
The first fix I tried back is June was to make sure that the SharePoint Site that I was using was added to the Local Intranet Site in Internet Explorer. Then, to make sure that Intranet Sites were passing my credentials through IE. It worked for about two or three weeks but then I started getting the logon box again.
Still plagued with the whole challenge dialogue box I had to find another solution. I came across This Blog, from the Microsoft Office Products Groups that has finally addressed this problem. Once I made the changes to my Connections Settings and added the "Fake Proxy" as described in this article I stopped receiving the challenge message.
This is one of those small fixes that will totally improve user experience and SharePoint acceptance. I would definitely try follow this workaround if you or your client is experiencing this error.
