Infinte loop problem

Having problems with some php

Attempting to:

if in certain parent category, dynamically get the child category then list it’s posts or if in other parent category display something else.

My bad php is letting me down and I’m creating an infinite loop – could someone please set me right

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

			  <?php if (in_category('something')) { ?>

                                <?php
                                if (is_category( )) {
                                  $cat = get_query_var('cat');
                                  $yourcat = get_category ($cat);
                                 }
                                ?>

                           		<?php query_posts('category_name='.$yourcat->slug.'&showposts=20'); ?>
                                <li><a href="<?php the_permalink(); ?>">
                                <?php the_title(); ?>
                                </a></li>

				<?php } else { ?>

                <?php dynamic_sidebar( 'primary-widget-area' ); ?>	

                <?php } ?>

   <?php endwhile; ?>