Additional Column in Blog Post Listing

Hi there
I have attempted to implement adding a new column to the blog post listing as per the link below.
http://www.sitefinity.com/blogs/lubomir-velkovs-blog/2012/01/22/extending_the_built-in_content_modules
The site builds OK, however when selecting a blog to view posts we now get an error as follows:
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"NetworkError:  404 Not Found -
localhost:60876/.../
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Are you able to provide any feedback on where to start looking / what is wrong.
We are running V6.1. I have updated the columns under Admin - Settings, updated the global.asax which is evidenced in the above error.
One thing I do note is that there is no Interface class for the ExtendedService included in the zip download - should there be one ?

Thanks
Nigel