All was fine until I fired up the Sitecore Page Editor to work on some of the site content. What greeted me after I logged in was quote literally an empty page. The Chrome Dev Tools confirmed that the page requested had indeed returned a zero byte response. I faired no better when I tried to preview the page in the Sitecore Content Editor, I just got the same story, an empty page. The odd thing was that when I hooked up the Visual Studio debugger I could see that all of my MVC layouts, controllers and renderings were executing just as I expected. When this sort of thing happens I usually fall back to chopping out anything that could be interfering with the response, in this case pipeline handlers and finally modules. Eventually the culprit revealed itself, the CassetteHttpModule was responsible for my empty responses.