If the ASPxMenu control in which the RenderMode property is set to Lightweight, has a fixed Width and this width is not enough for item images, text and "arrow" divs, then you will see the following unexpected effect:
The following solution allows you to eliminate this effect:
1) Set the CssClass property for the ASPxMenu control;
2) Set the ItemStyle.Wrap property of the menu item to true;
2) Create css rules for internal divs that have the "dxm-content" and ".dxm-popOut" CSS classes. Their total widths and paddings should be less than or equal to the Width of the ASPxMenu