Disable your firewall(s) and antivirus(s). If that does not work, open up command prompt (Start->Run->type Cmd), and then type:
ipconfig /flushdns
ipconfig /renew
If that does not work, try re-installing the client.
If that does not work, please install Team Viewer(
www.teamviewer.com), and PM me the ID/Pass, and I will be able to assist you further.