I use InheritedResources a fair bit in apps that I build simply because it makes it quick to get up and running.  It allows for faster setup because you don't have to write anything for the typical CRUD.  I particularly find it useful with JSON, until yesterday.

I rely on the server to build the HTML and return both the object and html in the json (when needed).  In doing this I added the line

success.json { render :json => {:object => resource, :html => render_to_string(:partial => 'resources/resource_row')} }

The exception occurs in trying to render the partial.  There is not resource_row.json, just html.  The problem I found was that it was swallowing the exception and returning the default response which in json case, was just the resource standard to_json

So, hopefully I can patch it so that it won't swallow the exception and leave others chasing the issue.  In the meantime, if you have something standard coming back even though you have overode the default, check if it is throwing an exception.