Try the steps in the link below:

http://support.microsoft.com/kb/956196

I usually try this first..

1. Temporarily disable any firewalls on your computer.

2. Click on Start-Run, then type "cmd", then click on OK. When the command window loads, type:

ipconfig /release

(Be sure to leave a single space between "ipconfig" and the forward slash)

then press the "Enter" key.

Now type:

ipconfig /renew

then press the "Enter" key again.

Hope this helps.

Grif