This might work.
Go to command prompt : XP : press on start, then "Run", then type in "cmd" and press Enter.
Vista + 7 : Press on start and in the search box, type in "cmd" and press Enter.
When inside command prompt, type in "net stop dnscache" and press enter. This turns off the dns client service. (don't worry, it turns on after you turn your computer back on, and you don't need to do this again).