Run Time error 1004 in Excel Macro

I have the following macro written within Excel 2003 and it works fine. I am not sure as to what was the original version of Excel in which this was written.
However, a user complains that he gets a run time error 1004 as "The cell or chart you are trying to change is protected and therefore read-only ........" in his machine that runs Excel 97/2000.

Here is the code snapshot:
Public Sub PasteForecast()
Sheets("Error History").Visible = True
Sheets("Error History").Select
Range("A2").Select
Do Until ActiveCell.Value = Sheets("2) Forecast Worksheet").Range("C3").Value
ActiveCell.Offset(1, 0).Select
Loop
ActiveCell.Offset(0, 2).Select
Sheets("2) Forecast Worksheet").Range("C20").Copy
Sheets("Error History").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False

The code fails in the last line.

The Error History sheet is Hidden and it has some cells as write protected like Columns B,G,H,I,J etc.

Thanks in advance.

Of course you understand that you cannot copy to protected sheets or cells without unprotecting them, you could unprotect the sheet first...Sheets("Error History").unprotect as long as you dont have a password.

Regards,
Simon