I have tried that as well but the menu is still closed at once. But if i set the property ClickToOpen to false the menu stays open. But that is not the behavior i want. Try it yourself, I try to open the menu like this:
<
a href ="#" onclick="openRadMenu('<%=radmenu1.clientid %>');">AA</a>
function
openRadMenu(menuId)
{
var oRadMenu = $find(menuId);
oRadMenu.get_items().getItem(0).open();
}