The DNSChanger malware that has been effectively neutralized by the take over of the Estonian servers hosting the rogue DNS servers will have a sting in the tail for those still infected when the servers are switched off on 9 July 2012 – no access to your favourite web sites or any service that requires a DNS lookup – in practice nothing will work.
Forbes have published a story from the FBI regarding this – note that DNSChanger affects Macs too. Some direct advice from the DNSChanger Working Group (DCWG) is here.
To check whether you are infected, use the DNSChanger Check tool that is linked to from the DCWG – if you are infected then you have until 9 July to disinfect your computer.