Unwanted Edges cutting models

As can probably tell, i’m very much a newbie to this software. But, some how I keep getting a sharp edge at base of neck on character models i’m atempting to make. I’ve been following lesson vids on how to make a basic models as closely as possible. At first wasn’t any problem, I blended from neck down into torso no problem. However, recently it’s began making a harde edge at base of the neck. I’ve using smooth tool, but it doesn’t seem to do anything and increasing poly just shows it with like someone taking a razor down along the edge lines and cutting it clean off… I have tried so far just plain restart from scratch and it still came up again! I even deleted all the edges and vertexes in area and tried making whole new faces to snap it all together and it still had that sliced look to it.

Does anyone know what i’m doing wrong or is this some weird glitch I’ve stumbled on?
Currently using Blender 2.56 release

It’s not entirely clear to me what “a sharp edge” is here. My guesses:

  1. In edit mode, select all and Ctrl+N to recalculate normals.
  2. Maybe you’ve marked that/those edge[s] as sharp. In edit mode, select all edges /or just those affected) and Ctrl+E→Clear Sharp.
  3. If you’re using a subsurf modifier, you might have set a crease to the edge[s]. Select the edge[s] and in the properties panel [N], reset the crease to 0.

Well, after I reset the program and came back later, the problem just disapeared on it’s own. Never changed any settings, it just disapeared from the model.