If you installed .NET Service Pack 1 you might notice that certain RSS feeds are broken and might return an HTTP Protocol Error. As Dare suggests , this is due to the fact that the HttpWebRequest class has been modified to make it more compliant to the HTTP spec. E.g. on the MS research feeds, this errors because the server returns the Content-Location header as “Content Location” (notice the space as opposed to the hyphen). You can check out the <strong>list of fixes</strong> in .NET SP1.