Runtime error '28'..... out of stack space solution!!

Hey friends!!

Private Sub Worksheet_Change(ByVal Target As Range)
If Range("A4").Value = "GRTP" Then
    Range("A5:P47").EntireRow.Hidden = True
    Range("A127:P164").EntireRow.Hidden = False
ElseIf Range("A4").Value = "MMIT" Then
    Range("A5:P47").EntireRow.Hidden = False
    Range("A127:P164").EntireRow.Hidden = True

End If
End Sub

I have the above code, every thing goes well.. but when i add

Range ("A1").Value = "ASIA"

after

If Range("A4").Value = "GRTP" Then

Then i have a runtime error '28'... out of stack space and excel shuts down itself..
What is my problem... can anyone help me with this??

Thanks