Query Custom Post Types & category_name?

I’m using jQuery Supersized to create a full screen image slideshow. The images are called from a custom post type called Slides.

The code works fine but I want to be able to only pull in Slides in a specific category and for some reason I can’t get this to work.

I’ve tried adding ‘&category_name=’ to the first line to this but it’s not working:

query_posts('post_type=slides&category_name=project1&order=ASC&posts_per_page=-1');

Any ideas?

Thanks

query_posts('post_type=slides&order=ASC&posts_per_page=-1');
$output = "";
$n= 0;

//Loop for Post Types Slides
if ( have_posts() ) while ( have_posts() ) : the_post();
$n++;

//Slide Image
$thumbnail = wp_get_attachment_image_src(get_post_thumbnail_id(), 'full');

//Get the Slide meta info
$slide_link = get_post_meta(get_the_ID(), 'mb_slide_link', true);

$output.="{";
$output.="image : '". $thumbnail[0] ."'";

if($slide_link != ''){
$output.=" , url : '". $slide_link." '";
} ;

$output.="},";