"V" " No edges could be ripped" error message

I am doing a tutorial here: http://cgcookie.com/blender/cgc-series/weapon-modeling-an-m4/ At a certain point in the video he says to press “V” to separate out an unwanted edge before moving a vertex. I get an error message “no edges could be ripped.” Can someone tell me what I am doing wrong?

Where I get the error message “No edges could be ripped.”

From the tutorial. This is what I get because I can’t separate out the unwanted edge.

From the tutorial. This is what is supposed to happen:

Link to my Blender file:

Link to the tutorial Blend file*:

*Note: He does a whole lot of subsequent topology changes to this part of the rifle, so I don’t know if seeing the file will help someone to tell me what I am doing wrong.

Make sure that you have just the single vertex selected when you press V.

By the way, the ripping tool is a bit tricky to use. The result depends on mouse position around the selection.
It can work with more than a single vertex selected, but it can at most be a line of connected edges. I would recommend you to try playing with it on a different model (subdivided cube etc.) to understand how it behaves before you use it for modeling.

(Sorry, I didn’t watch the video, hope it doesn’t matter)

Thanks for responding. As far as I know there is only one vertex. I ended up deleting the line segment and extruding the vertex to recreate the edge. It seemed to have solved the topology issue mentioned in the tutorial. This tutorial is a little too advanced for me. The video is only available with paid “citizen” membership, anyway.