I think the issue is related with the gap that is between the first and the second level.
If you open your menu.css file, please change this class:
ul#cssmw ul.level-1 {
left:0;
padding:1px 0 0;
top:100%;
}
to
ul#cssmw ul.level-1 {
left:0;
padding:0 0 0;
top:100%;
}
Let me know if you still have any other questions.