Primary Links Drop Down

I'm using about theme through aboutpeople. I have the hierarchy set up in the primary links menu configuration but its not working. I'd like to have the child items show upon mouse-over. I have 2 tiers below the main if that makes a difference. How can I make this function work? I'm guessing I need to edit my page.tpl.php and change:
print theme('links', $primary_links, array('class' => 'links primary-links'))
But I'm not sure what to change it to. I've tried many of the recommendations in support searches for other themes, but none seem to work. Help would be much appreciated!
Thanks.