ButtonList SelectedIndexChanged event not firing

This is another one I don't understand.  I have the following button list control in a page:
 <asp:RadioButtonList ID="reportLevelList" runat="server" AutoPostBack="true"
                            onselectedindexchanged="reportLevelList_SelectedIndexChanged">
                            <asp:ListItem Enabled="true" Selected="True" Text="Opportunity Reports By Sales Person" Value="sales"></asp:ListItem>
                            <asp:ListItem Enabl ...