I have been noticing this issue for some time, and have not found a clear answer as to its cause. I have a 2003 server with AD environment running about 60 workstations. I have been noticing over the past several weeks that my Local Area Connection says Authentication failed. However I am still able to access all of my network resources and the internet. I am running Vista Ultimate 64bit with SP1. Any information anyone can render will be appreciated.