Simplepress navigation menu problem

Hello,
I have an issue on my blog,
I m using SimplePress (a template from Elegant themes)and on the home page, the navigation menu on top seems to be different from the other menus on the pages.
It doesnt show the subcategories when I pass the mouse on the titles and when I do the same on a regular page it works.
Plus the menu is positioned on the left in the Homepage and centered in other pages.
Could anybody help me?
I tryed to reorganize the menus myself going on Appearance ==> Menu
It follows the order of menus I choose but still no subcategories appear…