Application-defined or object-defined error

Hello,

I made a script that sorts a range of cells and deletes rows that do not
comply with a condition. I get this error in Excel 2003 but I don't get it in
Excel 2007.
The debug highlights this line as location of the error:

ActiveSheet.Range(ActiveSheet.Range(first.Offset(stp, 0)),
ActiveSheet.Range(last.Offset(-1, 66))).Select

and the line is part of this context :

rownum = last.Row - first.Offset(stp, 0).Row
i = 1
Do While i <= rownum
Set rowx = ActiveSheet.Range(last.Offset(-i, 0), last.Offset(-i,
66))
If Application.WorksheetFunction.Max(rowx) = 0 Then
rowx.Delete shift:=xlShiftUp
rownum = rownum - 1
Else: i = i + 1
End If
Loop

ActiveSheet.Range(ActiveSheet.Range(first.Offset(stp, 0)),
ActiveSheet.Range(last.Offset(-1, 66))).Select
Selection.sort Key1:=Range(first.Offset(stp, 0), last.Offset(-1, 0)),
Order1:=xlAscending, Header:=xlNo, _
OrderCustom:=1, MatchCase:=False, Orientation:=xlTopToBottom, _
DataOption1:=xlSortNormal

This is a sorting script recorded with the macro recorder. first and last
are 2 range type variables which are set when the sub is called by another
sub, stp is an integer set also when the sub is called (it's value may be 2
or 3).
rownum and i are local integers and rowx is a local range.

I tried the 2007 sort method and the 2003 sort method and got errors but
just in Excel 2003. If you have any ideea how I could make this error
dissapear in Excel 2003, please tell me.

Thank you,