Can you ensure that you're running the game as an Administrator?
On Windows 7 and Vista you can check that the game has administrator privileges, by right clicking on the shortcut to the game and choosing Properties. Then choose the Compatibility tab, and finally choose Run this Program as an Administrator.
OK this screen, then try the game again.
If that doesn't help, make sure your Internet Explorer installation is working correctly and isn't set to Offline mode, and that you have the latest Windows updates from here:
Threats of violence. We take these seriously and will alert the proper authorities.
Posts containing personal information about other players. This includes physical addresses, e-mail addresses, phone numbers, and inappropriate photos and/or videos.
Harassing or discriminatory language. This will not be tolerated.