These may sound like silly questions, but 1. Does your page have an .aspx extension? 2. Have you installed ASP.NET on your server? If both of those are "yes", then it sounds like someone may have tampered with the ISAPI mappings for IIS. These are not silly questions. Yes. Yes. The only thing I have been able to learn from Google is, just as you have confirmed, is that this has something to do with the ISAPI mappings. But, where on earth do I go from here?