Open polylines are changed to rectangles when you edit picture

When you insert a vector graphic, such as a WMF (Windows Metafile) or CGM (Computer Graphics Metafile), into an Office document and then edit the picture in the Office Picture Editor, open rectangular polylines (shapes that look like a rectangle with one side missing) are changed to closed rectangles.

Steps to Reproduce Problem

1. In Word 97, create a new blank document.
2. Run the following macro to insert an open rectangular polyline:

   Sub Polyline1()
   Dim myArray(1 To 4, 1 To 2) As Single
   myArray(1, 1) = 100
   myArray(1, 2) = 25
   myArray(2, 1) = 20
   myArray(2, 2) = 25
   myArray(3, 1) = 20
   myArray(3, 2) = 110
   myArray(4, 1) = 100
   myArray(4, 2) = 110
   ActiveDocument.Shapes.AddPolyline myArray
   End Sub
   					

   
   
3. Select the polyline.
4. On the Edit menu, click Copy.
5. On the Edit menu, click Paste Special. Select As Picture and then click OK. This pastes the clipboard contents as a WMF into Word.
6. Right-click the picture, and then click Edit Picture on the shortcut menu.

In the Picture Editor, the polyline is changed to a rectangle.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.