Today, I found an SBS 2008 box that was not resolving a certain web site. The client had gone to that site before, but today they could not. The client was on-site with the server and set only with the SBS box as the DNS server. I couldn't run a tracert to the site (from a DOS prompt on the server) - it said unable to resolve target (I believe). After troubleshooting, all I did was stop and restart the DNS Server service. Very dumb.
Perhaps this article might have helped, I don't know.
But it was next on my list of things to try.