Hi there.
I have been experiencing some mesh problems when modelling using the extrude tool, to extrude edges.

I have followed this series of tutorials, and copied everything the tutor has done almost perfectly. Yet still I am faced with this problem, where none exists in the tutorial video. I am also using the exact same version of Maya. This also happened when building up the torso. I have tried deleting faces and re-extruding those edges, but to no avail.

Here is the video: https://www.youtube.com/watch?v=E9wehgCLS0w

See below the images to illustrate what I am referring to.

Does anyone know what I'm doing wrong? Any help much appreciated.