Pagination gives extra page with no results

I’m trying to implement pagination on a category page. The pagination is working, but now for some reason the pagination plugin I’m using is noting one extra page of results, when that page is actually empty.

I’m pretty sure it doesn’t have anything to do with the pagination plugin because I’ve seen reports of people having the same problem with next_posts_link and previous_posts_link.

Anybody have any idea how this could happen?

Loop:

<?php       
global $myOffset;
$myOffset = 11;
$temp = $wp_query;
$wp_query= null;
$wp_query = new WP_Query();
$wp_query->query('offset='.$myOffset.'&cat=6&posts_per_page=12'.'&paged='.$paged);
?>

<?php while ($wp_query->have_posts()) : $wp_query->the_post(); ?>

STUFF

<?php endwhile; ?>

<?php if(function_exists('wp_paginate')) {
   // get yo paginate on
   wp_paginate();
} ?>

Edit:
I am also using this functions.php plugin to enable the offset parameter in a custom wp_query:

function my_post_limit($limit) {
    global $paged, $myOffset;
    if (empty($paged)) {
            $paged = 1;
    }
    $postperpage = intval(get_option('posts_per_page'));
    $pgstrt = ((intval($paged) -1) * $postperpage) + $myOffset . ', ';
    $limit = 'LIMIT '.$pgstrt.$postperpage;
    return $limit;
} //end function my_post_limit