There are a few possible causes to this issue.
1. Static IP settings on the user account that is not broken.
2. Proxy settings on iyour web browser
3. Firewall/Internet security issues.
Some more information will be needed, we can start with the firewall as that is easiest.
If you use something like norton or mcafee try right clicking the icon (lower right by the time) there is usually an option to disable the firewall. Try disablng that.
As far as proxy settings, what web browser are you using? Internet explorer, firefox, chrome?
To fix static ip issues, follow the following procedure
Click Start->Run
Type ncpa.cpl and press enter
Right click on the Local Area Network Connection
Click properties
Click Internet Protocol (not the check box click the words so it highlights)
Click properties make sure that the selected boxes are the "automatically detect" options, for both ip address and DNS
If they are not, select them, if they are close out all of those windows and move on.
Let me know how it works out,