Try it like this...
Code:
Option Explicit

Private Sub Form_Load()

    Dim oSld As PowerPoint.Slide
    Dim oShp As PowerPoint.Shape
    Dim objPpt As PowerPoint.Application
    
    Set objPpt = CreateObject("PowerPoint.Application")
    objPpt.Visible = True
    Set objPres = objPpt.Presentations.Open("C:\Documents and Settings\u173934\Desktop\BSA-AML Production Flash Report.ppt")

    For Each oSld In objPpt.Presentations.Item(0).Slides  'it fails on this line
            For Each oShp In oSld.Shapes
                If oShp.Type = msoLinkedOLEObject Then
                    oShp.LinkFormat.Update
                   End If
                Next oShp
            Next oSld
    End Sub
End Sub