I notice the same thing sometimes if I take too long to get to the drop down menu. You might try decreasing the delay time before the menu closes after you stop hovering over it, if that's an option you have. Hope that helps. Site is looking good. Have you decided not to use the nav buttons, or are you going to add them later?
-Mike
***Edit***
Looks like you can change that at the top of your hover.js file.


