im using theme called pinpoint, as far as i know the menu is part of wordpress and not the theme, am i correct? using 3.7.1. here is link to the page: http://www.teamsupport.co.za/web
The way the menu displays is controlled by the theme.
Looks like this might work:
.sub-menu {
max-height: 200px;
overflow: scroll;
}
For additional help, please contact the developer of your theme, as commercial themes aren’t supported on these forums.