showposts=-1 crashing loop

Since I upgraded to 2.8.4 I seem to be having a problem with a page that creates an archive listing by using a query using showposts=-1&cat=3. It seems to be an interaction with some of the plugins, SEO and wp-polls but I can’t work out what. It seems to be something with running to the end of the posts as if is use 500 instead of -1 it works fine but if I use 1000 it fails in the same way as with -1. Any help would be appreciated.

Here is the code:

<?php get_header(); ?>

	<div id="content" class="narrowcolumn">

    <?php if (have_posts()) : ?>
    	<?php $post = $posts[0]; // Hack. Set $post so that the_date() works. ?>

		<?php
		$current_month = get_the_time('m');
		$current_year = get_the_time('Y');

		if ($current_month != date('m') || $current_year != date('Y')) {
			/* This is an archive not current month*/
			echo '<h2 class="pagetitle">News Archive for ' . get_the_time('F, Y') . '</h2>';
		} else {
			echo '<h2 class="pagetitle">In the News This Month:</h2>';
			$current_month = date('m');
			$current_year = date('Y');
		}

		query_posts("cat=3&year=$current_year&monthnum=$current_month&order=DESC&showposts=-1");	

		?>

		<ul>
		<?php while (have_posts()) : the_post(); ?>

                    <li><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>"><?php the_time('d/m/Y') ?> - <?php the_title(); ?></a></li>

		<?php endwhile; ?>

		</ul>

<h2>News Archive:</h2>
<ul>
<?php
		$ArchYear=0;
		$ArchMonth=0;
		//echo '<li>hello</li>';
		//query_posts("cat=3");
		//$archive_query = new WP_Query('showposts=-1&cat=3');
		$archive_query = new WP_Query;
		$archive_query->query('showposts=500&cat=3');
		while ($archive_query->have_posts()) : $archive_query->the_post();
			//echo '<li>' . get_the_time('m') . '</li>';

			if (get_the_time('Y') != $ArchYear) {
				if ($ArchYear != 0 ) {
					echo '</ul></li>';
				}
				echo '<li>' . get_the_time('Y') . '<ul>';
				$ArchYear = get_the_time('Y');
			}
			if (get_the_time('m') != $ArchMonth) {
				$ArchMonth = get_the_time('m');
				echo '<li><a href="/news/' . $ArchYear . '/' . $ArchMonth . '">' . date('F', mktime(0,0,0,$ArchMonth,1)) . '</a></li>';
			}

		endwhile;
?>
</ul>

	<?php else : ?>

		<h2 class="center">Not Found</h2>
		<?php include (TEMPLATEPATH . '/searchform.php'); ?>

	<?php endif; ?>

	</div>

<?php get_sidebar('news'); ?>

<?php get_footer(); ?>