Go Start>Run (Start search in Vista), type in:
cmd
Click OK (in Vista and 7, while holding CTRL, and SHIFT, press Enter).
In Command Prompt window, type in following commands, and hit Enter after each one:
ipconfig /flushdns
ipconfig /registerdns
ipconfig /release
ipconfig /renew
net stop "dns client"
net start "dns client"
Restart computer.