Hi,
I'm not able to replicate that problem using the latest version of mojoPortal and the latest version of the artisteer31-hovermenu skin. I am testing with IE 10 using IE 9 mode.
I know I did fix something in that skin related to the admin menu not long ago so make sure you are using the latest version of mojoPortal and copy the latest version of that skin from /Data/skins to /Data/Sites/1/skins
Though the problem I fixed was in other browsers, I've never seen the problem shown in your screen shot.
If all else fails you could always remove the entry for the admin menu from the style.config file, then it will just be a vertical list.
Hope that helps,
Joe