Remove Home tab

I'm not quite sure I follow your explanation really - looking at your URL I don't see a Home post or a second Home tab. I just see the Home link on your menu bar and to me (without seeing your Wordpress pages setup) I would say that you just don't have a page called "Home" and that is why the 404 error is showing on the homepage.

Make sure that you have a "Home" page created and then take a look at the Settings > Reading options in the WordPress Admin  If you want your new "Home" page to display as your actual homepage then choose the Static Page option.

You can also control where your main Menu Bar navigation links point to by building an actual WordPress menu in Appearance > Menus in the WordPress Admin. This is going to kind of rely on some things in Artisteer however because your theme (that was created with Artisteer) will need to support WordPress Menus which is a relatively new feature in WordPress.

It's been a while since I have used Artisteer - it just seemed to become rather clunky and more work than purchasing a premium theme that just works.