Getting run time error on some Win7 computers but not others with VB runtime

Run-time error 2147319765 (8002802b)  Automation error Element no found

I use visual basic 6 in windows 7 to operates outside of an autocad 2007 program.  My visual basic program works perfectly well on some identical computers but throws the error noted above on two other similar computers!

The project is referenced to Autocad 2007 Type Library.

The program I wrote simply requests an autocad screen then asks the user to select a polyline.  The error then appears in the line highlighted in my code below:

Private Sub Command1_Click()
Dim plobj As AcadLWPolyline
Dim ssetObj As AcadSelectionSet
Dim myapp As AcadApplication
Dim mydoc As AcadDocument
Dim i As Long
Dim ent As AcadObject
Dim ppt As Variant
Dim pcount As Long
Dim clObj As AcadLWPolyline

On Error GoTo err:

''List2.Clear
''List3.Clear
''List4.Clear
''List5.Clear
''List6.Clear
''List7.Clear
''
''List8.Clear
''List9.Clear
''
''Grid1.Clear
''Text1.Text = ""
''
''On Error GoTo err:

Set myapp = GetObject(, "Autocad.application")
Set mydoc = myapp.ActiveDocument

    If mydoc.SelectionSets.Count > 0 Then
    mydoc.SelectionSets(0).Delete
    End If

Set ssetObj = mydoc.SelectionSets.Add("sent")

On Error Resume Next
AppActivate ("Autocad")
    If err Then
    Me.Show
    MsgBox "Is Autocad Runnning - it should be!", vbOKOnly, App.Title
    Exit Sub
    End If
            
On Error Resume Next

myapp.ActiveDocument.Utility.GetEntity ent, ppt, "Select Centerline: "[u] ***********************************************ERROR HERE*******************[/u]
    If err Then
    Me.Show
    MsgBox "Nothing Selected1"
    Exit Sub
    End If

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-------------------------------------------------- more code below that I can send but seems not to be at issue ---------------------------