My web application menu isn't showing in any browser I use to test.

I looked around and checked out if it wasn't the z-index bug mentioned here, that seems to have caused some trouble to many people. I'm wondering if I'm doing something wrong:

<asp:Menu ID="Menu1" runat="server" DataSourceID="SiteMapDataSource1" Orientation="Horizontal" />
</asp:Menu>

I've got this as my SiteMap:

<?xml version="1.0" encoding="utf-8" ?>
<siteMap xmlns="http://schemas.microsoft.com/AspNet/SiteMap-File-1.0" >
  <siteMapNode title="Pagina">
    <siteMapNode url="Default.aspx" title="Home" description="Página Inicial" />
    <siteMapNode url="Generos.aspx" title="Géneros" description="Géneros"  />
    <siteMapNode url="Artistas.aspx" title="Artistas" description="Artistas" />
    <siteMapNode url="Musicas.aspx" title="Musicas" description="Músicas" />
    <siteMapNode title="Admin" roles="Administrador">
      <siteMapNode url="Admin/Musicas.aspx" title="Musicas"/>
    </siteMapNode>
  </siteMapNode>
</siteMap> 

Any suggestions about what might be wrong?

TIA