MOSS 2007: cannot delete a question in a survey (Unknown Error)

Problem: In a MOSS 2007, when try to delete a question in a survey a message saying Unknow Error (before SP2) or Unable to validate data.   at System.Web.Configuration.MachineKeySection (after SP2) is displayed.

Resolution: in the web server browse to the path C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS, open the file mngfield.aspx (if MOSS is not installed in the default paths, browse for the file) in Notepad and add the following line:

<asp:Content ContentPlaceHolderId="PlaceHolderSearchArea" runat="server">
</asp:Content>

We have MOSS installed in a front end server and the database in a backend server. I don´t know if other configurations this solution could work.