I would bring up the Animation Palette and look for the walk cycle. If you are lucky it maybe on a Layer of its own or it might be an Animation Set.  If it is one of those two then it should be a simple matter of deleting that Layer or Set and resaving the scene/pose.  If you are unlucky then it maybe part of the Key Frames in which case you will have to go into to each part of the body that you want to stop moving and delete the keyframes for that part.

 

I have not looked into a Pose file directly, however a quick test in  poser 6 and 2014 seem to indicate that an animated pose is saved as a set of some kind.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13