"index is out of range" error, but only when data is loaded into a form

Here's the situation: I have a web form that takes company information.  Part of the form contains sections that are displayed or hidden based on a Listing_Level field. 
<asp:ScriptManager ID="List_Level_Updater" runat="server"></asp:ScriptManager> <div> <asp:Label ID="Listing_Level_ID_Label" runat="server" Text="Listing Level:" AssociatedControlID="Listing_Level_ID"></asp:Label> <div class="form-field"> <asp:DropDownList ID="Listing_Level_ID" runat="server" OnSelectedIndexChanged="ShowCatsLogosDescExpiryDate" AutoPostBack="True"> </asp:DropDownList> </div> <div class="cleft"></div> </div> <div> <asp:L ...