The SessionInit cause a stack overflow using this code:

public class SessionManager implements org.zkoss.zk.ui.util.SessionInit {

public void init(Session arg0, Object arg1) throws Exception {

String serverName = arg0.getServerName();
Skin defaultSkin = null;
Skin currentSkin = null;
for (int i = 0; i < SkinManager.getSkins().size(); i++)

{ Skin skin = SkinManager.getSkins().get(i); if (skin.isDefaultValue()) defaultSkin = skin; if (serverName.contains(skin.getURL())) currentSkin = skin; }

if (currentSkin == null)
currentSkin = defaultSkin;
if (currentSkin!=null)
arg0.setAttribute("SKIN", currentSkin);

String SQL = "SELECT TO_CHAR(sysdate,'YY') || TO_CHAR(next_day(TRUNC(sysdate)-7, TO_CHAR(to_date('27-09-2011','DD-MM-YYYY'), 'Dy')) ,'IW') AUX FROM dual";
DAO service = new DAO();
List<Map<String, String>> rs = service.getListData(SQL);
arg0.setAttribute("palinsesto", ((Map<String, String>) rs.get(0)).get("AUX").toString());
}

You can find the stack trace here:
http://www.zkoss.org/forum/listComment/18598-Session-stack-overflow