in your archive.php file, inside your loop, you will see a group of codes something looks like this:
<h2><a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a></h2>
<p class="post-info">Posted by <?php the_author_posts_link(); ?> | Filed under <?php the_category(', '); ?></p>
<p><?php the_content('Read more'); ?></p>
<p class="post-footer"><a href="<?php the_permalink(); ?>" class="readmore">Read more</a> | <a href="<?php comments_link(); ?>" class="comments">Comments (<?php comments_number('0','1','%'); ?>)</a> | <span class="date"><?php the_time('F j, Y'); ?></span></p>
try to compare you codes, if you notice, <?php the_content('Read more');?> is missing in you code. Put them into yours.
hope this helps