We've got an older ASP.NET WebForms website, currently written in VS 2010. It's running on a Windows 2003 R2 server, so it's in IIS 6. Recently we've had users call, saying that one of the pages doesn't work. It just happens to be the only page on the website, that uses the FormView control. When the user clicks on the New button to begin entering data, nothing at all happens. Some of the users have said that it doesn't work on older versions of IE, so that would imply that they're not running it on Windows 8. But other users have said that it doesn't work on IE10. At work I have IE10, but that's on a Windows 7 machine, and it works fine there. At home I've got Windows 8, and of course IE10, so I tested it from home, and sure enough it doesn't work in IE10 on Windows 8, both the Metro version of IE10 and the desktop version of IE10. I brought up Fiddler, allowed it to work with HTTPS, and tested it. When I did I found an error of 500. Looking that up on Wikipedia I get a rather unhelpful description that says, "Error A generic error message, given when no more specific message is suitable".
Bottom line, what's wrong and how do we fix it, given our current server configuration?