It worked for me, and I added a condition to check for any under sized lines. I work with some old CNC machines and parts will bomb if you have small line segments. So this can be used to check parts first.

Thanks,
Rob

     'check for under sized lines
     If acLine.Length < 0.125 Then

          Dim midp As Point3d = acLine.GetClosestPointTo(acLine.GetPointAtParameter(acLine.EndParam / 2), False)
          Dim vec As Vector3d = ed.CurrentUserCoordinateSystem.CoordinateSystem3d.Zaxis
          'set radius to .25
          Dim circ As Circle = New Circle(midp, vec, 0.25)
          'drop some properties
          circ.Layer = "0"
          circ.ColorIndex = 1
          circ.LineWeight = LineWeight.LineWeight050
          btr.AppendEntity(circ)
          tr.AddNewlyCreatedDBObject(circ, True)

       End If