Please do the followings :
1. Click Start -> Run -> Type "cmd"
2. in command prompt box, type "ipconfig /flushdns"
3. Change your DNS into one of these 2 DNS server
Google DNS : 8.8.8.8 and 8.8.4.4
DNSAdvantage : 156.154.70.1 and 156.154.71.1
4. Here's the tutorials if you haven't known how to do it.
for windows XP :
http://www.mediacollege.com/computer/network/dns.html
for windows Vista :
http://windows.microsoft.com/en-US/windows-vista/Change-TCP-IP-settings
for windows 7 :
http://windows.microsoft.com/en-US/windows7/Change-TCP-IP-settings
If you have any more queries, please let me know.
Best Regards,
Diko Nuisance - NewRapidLeech.com