Working with query_posts ( arrays and query strings)

I’d suggest not using $query_string to simplify things. If you’re using an array, stick with the array form for the query variables:

global $wp;
$paged = ((int)get_query_var('paged')) ? (int)get_query_var('paged') : 1;
$s_array = array(
    'post_type' => 'blog',
    'caller_get_posts' => 1,
    'paged' => $paged,
    'meta_query' => array(
        array(
            'key' => 'votes_percent',
            'value' => '50',
            'compare' => '>',
            'type' => 'numeric',
        )
    )
);
$new_query = array_merge( $s_array, (array)$wp->query_vars );
query_posts($new_query);