This is a bug in the plus/minus "visibility" container object in DNN 3.2 and 4.0. You can easily fix the problem without recompiling - just locate /admin/containers/visibility.ascx, and edit the "enableviewstate" attribute of the LinkButton element, like this:
<%@ Control language="vb" CodeBehind="Visibility.ascx.vb" AutoEventWireup="false" Explicit="True" Inherits="DotNetNuke.UI.Containers.Visibility" %>
<asp:LinkButton ID="cmdVisibility" Runat="server" CausesValidation="False" enableviewstate="True">
<asp:Image ID="imgVisibility" Runat="server" enableviewstate="False"></asp:Image>
</asp:LinkButton>