This is rather like the issue referred to in http://www.mandeeps.com/Default.aspx?tabid=59&aff=27&aft=1514&afv=topic&language=en-US.
The menu drop-down, if it reaches as far as a Live Accordion pane, finishes up behind the pane rather than in front as one would want it to. No amount of fiddling with the z-index for the menu CSS will change this.
Site is DNN 5.5 running the default DNNMenu with Live Accordion 3.4.5.
Since there is a solution referred to in the post mentioned above but no clue what it may be, a pointer in the right direction would be appreciated.