Can you please be more specific? Are you getting this in Windows or by using the Forums Web App?
If this is from the Forums Web App what URL do you go to when you get this error? What is the user action you are taking if it is relative? Assuming this is not because you were able to post to the Forums.
If this is occuring in Windows try one of the Windows Forums:
http://answers.microsoft.com/en-us/windows/default.aspx#tab=2.
Hope that helps,
Jeff Willis