Nope, it’s not. It’s a bug, and has been fixed and will be available in the next version.
In the meantime, you can fix it by opening the theme’s index.php file. Then on line 25, replace this line:
$args = array_merge($wp_query->query, array('cat' => $cats));
with these lines:
$args = $query_string.$cats;
query_posts($args);