Custom post type preview fail

[elin....@gmail.com]

I'm using Magic Fields in a project and I've got multiple post types, including the front page. All post types works fine to preview and the url would be: "http://mysite.com/contact/contact_us/?preview_id=35&preview_nonce=XXXXXXXX&preview=true", which works fine for all the custom post types except the front page one. For the front page the preview url will be the same: "http://mysite.com/frontpage/example_post/?preview_id=61&preview_nonce=XXXXXXXX&preview=true" and since that is not the url to the front page, the preview doesn't work unless I remove "/frontpage/example_post" from the preview url. When I display the front page without preview it displays the front-page.php file which it's supposed to, but how can I change the preview-mode to also display the front-page.php instead of the actual post preview?