Windows 7 Error: Unable to resolve ip of host xxxx

[c a g a t a y]

Hi all
Last night I have upgraded my OS from XP to Win7
Everthing is OK
When I had tried to connect a web site (with Internet Exloper 8) I am getting Error: Unable to resolve ip of host Google
Google
FaceBook
etc
But I am connecting some other websites easily
Why I am not connecting to Google or FaceBook ?
What is the problem?

Regards