Try the following:
Sub InsertBlankRows()
Dim ColOfData As Integer
ColOfData = 1
For i = ActiveSheet.UsedRange.Columns(ColOfData).Rows.Count To 1 Step -1
If Cells(i, ColOfData) <> Cells(i + 1, ColOfData) Then _
Cells(i + 1, ColOfData).EntireRow.Insert
Next i
End Sub
Change ColOfData to the number of the column that holds your data (ie 1=A, 2=B)