If what Orbital Shark said here doesn't solve your issue follow the next steps:
1) go to start, type "cmd" in the search bar (without quotes), right click it and "run as administrator".
2) type this: "ipconfig /release" (w/o quotes) and press enter.
3) now type: "ipconfig /flushdns" (w/o quotes) and press enter.
4) now: "ipconfig /renew" and press enter.
If that doesn't solve it, do the following
1) type on the CMD window: "netsh winsock reset catalog" and press enter.
2) after done, type: "netsh int ip reset reset.log" and press enter.
Reboot and check if everything works!
And of course, report back... please