ASP.Net (VS 2005): This address is restricted in Firefox error December 16, 2007

Yesterday when I debugged my website in Visual Web Developer Express, I was greeted by this error “This address is restricted: This address uses a network port which is normally used for purposes other than Web browsing. Firefox has canceled the request for your protection”. There’s even a try again button but same result appear even though I clicked it repeatedly. For almost one year I’ve been using VWD 2005 Express for developing web application never once I’ve encountered such problem.