Fatal error: Call to a member function

I am trying to make a portfolio for my page and every time I try to goto it I get this error, Fatal error: Call to a member function have_posts() on a non-object in temp.portfolio.php on line 45

<?php
global $more;

// projects loop
$portfolio = new WP_Query(array('paged' => get_query_var('paged'), 'post_type' => 'project', 'posts_per_page' => get_portfolio('projects_per_page')));

$size = get_portfolio('image_size');

if($portfolio->have_posts()) : ?>

				<?php

				$_SESSION['portfolio'] = 'portfolio_2_col_s';

				if( isset($_GET['portfolio']) )
					$_SESSION['portfolio'] = $_GET['portfolio'];

				?>

				<ol id="<?php /* if( get_portfolio('sidebar')
										 && get_portfolio('num_columns') > 2) {
											echo '2';
										} else {
											_portfolio('num_columns');
										} ?>_col<?php if(get_portfolio('sidebar')) echo '_s';*/ echo $_SESSION['portfolio'];?>" class="portfolio_container">

<?php while($portfolio->have_posts()) : $portfolio->the_post(); $more = 0; ?>

The last line is line 45. For some reason it has worked once or twice, but then if I reload the page it gives me the error.