I recently migrated an ASP site from my dev machine to a live server. All the pages except my FAQ page works just fine, but my FAQ brings up:
XML Parsing Er
I had the same issue. It was caused because I handled exceptions in global.asax, and called Server.ClearError(), without calling a Response.Redirect or similar. I guess, that the code failed and the error was removed, so asp.net could not display an errormessage, nor could could it display the requested page.
I have also received this error, because I overrided the render method of the page, and forgot to call base.render(writer), thus sending an empty page to the browser.