As of AutoCAD 2004, VBA can no longer be used to explode non-uniformly scaled blocks although this could easily be done with earlier releases.

Test with the following snippet:

Sub ExplodeNonUniform()
    Dim oLine As AcadLine
    Dim oBlock As AcadBlock
    Dim oBlockRef As AcadBlockReference
    Dim StartPoint(2) As Double, EndPoint(2) As Double
    StartPoint(0) = 0#: StartPoint(1) = 0#: StartPoint(2) = 0#
    EndPoint(0) = 1#: EndPoint(1) = 1#: EndPoint(2) = 1#
    Set oBlock = ThisDrawing.Blocks.Add(StartPoint, "widget")
    Set oLine = oBlock.AddLine(StartPoint, EndPoint)
    Set oBlockRef = _
    ThisDrawing.ModelSpace.InsertBlock(StartPoint, oBlock.Name, _
      1, 2, 1, 0)
    oBlockRef.Explode
    '*** above line works in AutoCAD 2002, but not in 2004,5,6,7
    oBlockRef.Delete
End Sub
 

Workarounds: Assuming oBlkRef is the reference that you want to explode (and keeping in mind sendcommands own limitations):

thisdrawing.sendcommand ("explode" & vbcr & "(handent " _
  & Chr(34) & oBlkRef.Handle & Chr(34) & ")" & vbcr & vbcr)

First Appeared: AutoCAD 2004
Status as of 2008: Still reproducible
Status as of 2009: (unknown - please email with any info)