If you are still infected with the DNS Changer malware, you will be unable to access the internet as of July 9, 2012. According to the FBI, who took over a series of rogue DNS servers last November, there are still hundreds of thousands of computers infected with the malware. While the FBI substituted valid DNS servers to keep resolving internet names, these servers will be taken offline on July 9, making it impossible for infected PCs to resolve domain names.
You need to make sure your PC is not infected. You can do that by checking websites created by the DNS Changer Working Group (DCWG), a cross-industry team of experts. The list is posted here.
Sophos also provided an informative video:How not to lose your internet connection