The forum you posted to is for the discussion of Microsoft Security Essentials beta. This explains 403 errors -
http://en.wikipedia.org/wiki/HTTP_403 You need to provide more detail such as what you are trying to download, where you are trying to download from, and if the issue occurs on one specific website or all websites. Without having much detail my best guess for an appropriate forum to ask your question in would be the Internet Explorer newsgroups -
http://www.microsoft.com/communities/newsgroups/list/en-us/default.aspx?dg=microsoft.public.internetexplorer.general&cat=en_us_28cca3eb-7037-4d4f-bde1-d8efee1f1420&lang=en&cr=us
Jim - MVP Windows Live - Forum Moderator - Live One Care - Live Mesh - Microsoft Security Essentials