Chrome rendering dhtmlxMenu over an IFRAME

I can’t get this to work, any ideas? The IFRAME contains a pdf. The DHTMLX menu hides behind the IFRAME. This does not happen in other browsers i.e. MSIE/FF. See attached image/screenshot.

Has anyone had any success doing this? Is Chrome supported by DHTMLX or not? What about when dealing with iframes or framesets? i.e. Can the context menus be rendered above iframes and/or framesets?