security trimming with no roles

hi all,
I have a master page and a mySite.sitemap. I don't know what is wrong with my sql database setup, nevertheless the securityTrimmingEnabled in my web.config file does not do anything. Because I'm in a rush I would like to just hide/show menu items progarmatically based on my 2 possible roles my users can have. There is just one menu, two levels deep with just a few items each. For one role I need to show only two sub-items in the first item, all of them for the rest.
It is somewhat strange that Roles.Provider.GetRolesForUser("user1") is giving me the right value ...
Any idea how I hide menu items in my master page?
<form id="form1" runat="server"> <asp:SiteMapDataSource SiteMapProvider="WebSitemapProvider" ID="SiteMapDataSource1" runat="server" /> <div id="header"> </div> ...