register_post_type() and pagination error

Hi,
i create new post type with register_post_type() function.

Get posts by authors:

$args=array(
	'showposts' => $showposts,
	'paged' => $paged,
	'post_type' => 'cars',
	'author' =>  $curauth->ID
);

query_posts($args);

Everything works well, except last page.

I have 17 posts, displays 7 in page. And when i click on last (3 page),
I always get “nothing found” page.
Even is_author() function don’t recognize that is author page.