Harish's reply is accurate but probably needs more description. In short, you can't mix MVC and Web Form renderings/layouts. My situation was putting an MVC controller rendering into a layout using an .aspx page, ie Web Forms. I did a little write-up you can read here:
I don't know if this happens often enough that Sitecore should throw a more descriptive error. Also seems like a default Sitecore install should come with some sample MVC layouts and renderings, not just Web Forms.