Hi,
I am sorry, are you referring to the site linked from your username -> http://retail.kiik.com.au/wp-content/themes/propulsion/style.css ?
If that's the site, please put the following into Quick CSS located in Admin > Propulsion > Theme Options > Styling at the bottom of the page.
.main_menu .menu ul {top: 20px}
Your site looks great and the Super Cache plugin is doing its job on reloads, but its not using a correct configuration for the initial load. You are at about 7 seconds for first load and around a second for subsequent visits, which is one of the best I've seen - are you running on Nginx? But the first load you could drop down to 3 seconds easily.
Here is somethings you could do to make your site even faster which improves Google's ranking -> http://www.webpagetest.org/result/120923_RQ_3PQ/1/performance_optimization/ and
http://gtmetrix.com/reports/www.retail.kiik.com.au/caDt1bLH/pdf
Please let us know if the menu is behaving now.
Good luck,
Nick