DropDownList selection doesn't show

I've got two DropDownLists that are filled using a couple of SqlDataSources, like so:
<asp:SqlDataSource ID="dsCategories" runat="server" ConnectionString="<%$ ConnectionStrings:EPiServerDB %>" SelectCommand="img_GetCategories" SelectCommandType="StoredProcedure"> <SelectParameters> <asp:Parameter DefaultValue="1" Name="CountryID" Type="Byte" /> </SelectParameters> </asp:SqlDataSource> <asp:DropDownList ID="categories" runat="server" AutoPostBack="True" DataSourceID="dsCategories" DataTextField="Translation" DataValueField="CategoryID" Width="220px"> </asp:DropDownList> <asp:SqlDataSource ID="dsSubcategories" runat="server" Conne ...