I had the problem for two days. Several systems restores fixed the issue for a short period of time. Checked for viruses in safe mode with networking. Internet worked just fine in a safe mode with networking... I also tried to tweak Mcafee Internet Security that came with my Dell laptop. Disabling firewall and antivirus did not work. Downloaded a couple other virus malware killers and scanned in safe mode with no luck. They could not find anything. Finally I uninstalled McAfee... And voila! I installed Microsoft Security Essntials: it is free and my Internet works!!! I used to work in a call centre for Dell: problems with McAfee blocking the Internet were a real nightmare. So, if you have this issue with DNS server not responding, look...