Paste Special Method Error

[jds]

I am getting a macro error in Excel and would like to know if anyone can help me with the coding. The code is below. The error occurs on the last line of code

(Selection.PasteSpecial Paste:=xlDataValidation, Operation:=xlNone, _
        SkipBlanks:=False, Transpose:=False)

and gives me the following error:

Run-time error '1004'

PasteSpecial method of Range class failed

Sub test()
'
' test Macro
' Macro recorded 9/16/2008 by Computer User
'

'
    Application.Goto Reference:="R20C12"
    With Selection.Validation
        .Delete
        .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
        xlBetween, Formula1:="=INDIRECT($H$5)"
        .IgnoreBlank = True
        .InCellDropdown = True
        .InputTitle = ""
        .ErrorTitle = "Error"
        .InputMessage = ""
        .ErrorMessage = "You must enter a valid general ledger account number"
        .ShowInput = True
        .ShowError = True
    End With
    Selection.Copy
    Range("L21:L484").Select
    Selection.PasteSpecial Paste:=xlDataValidation, Operation:=xlNone, _
        SkipBlanks:=False, Transpose:=False

 

End Sub

Thanks in advance for any help