Am sure you have tried it, but have you tried rechecking your TCP/IP settings (gateway/DNS) etc?
Seems like the DNS info is wrong. Can you connect to:
http://64.58.76.229/ instead of
http://www.yahoo.com/
Are you using a router? Try filling in the DNS information manually as well.
In addition .. you mentioned you had DUN as well. Run 'winipcfg' and see what your network device is .. is it your PPP Adapter or is it your eth device? Switch to the eth device and connect. Always a good idea to remove any extra devices unused network devices that you may have.