You are trying to use code from the 2003 version which no longer applies

Try this (ON A COPY!)

Sub apply_CL()
Dim L As Long
ActivePresentation.Slides(1).CustomLayout = ActivePresentation.SlideMaster.CustomLayouts(1)
For L = 2 To ActivePresentation.Slides.Count
ActivePresentation.Slides(L).CustomLayout = ActivePresentation.SlideMaster.CustomLayouts(2)
Next L
End Sub