Problem category after upgrade

You probably have some plugin that does something with categories. All such plugins seem to raise problems in 3.1.

I have only this plugin that work with the categories:
WP No Category Base

But if i deactivate it my categories don’t work.

Is possbible that wp 3.1 have changed the codes? For example in my homepage this code don’t work:
<?php single_cat_title(); ?>

Orher problem is:

<div id="headline">
		<img src="<?php echo get_option('home'); ?>/wp-content/themes/arthemia/images/headline.png" />
		<?php query_posts("showposts=1&category_name=Headline"); ?>
		<?php while (have_posts()) : the_post(); ?>	

	<div class="title"><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></div>
	<div class="meta">[<?php single_cat_title(); ?> | <?php the_author() ?>]</div>
	<?php $values = get_post_custom_values("Headline");?>
 	<a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title(); ?>">
<img src="<?php echo catch_that_image(); ?>" alt="<?php the_title(); ?>" class="left" width="300px" height="275px"  /></a>

	<?php the_excerpt(); ?>
	<font color="#0000FF">Lee el articulo completo &raquo;</font>
	<?php endwhile; ?>
		</div>

Don’t see last “headline post” but appear the last post.

ALL this problem are connected with the category

Simple Tags plugin has been reported braking wordpress 3.1 categories. are you using it.
uncheck “Active tags for page” and everything will be ok

Guys i have the solution and i want share it!

Simple tag is the problem:

Go to simple tag and not flag it “Active tags for page:”

lol sorry keesiemeijer

I haven’t read you ?? Yes, thank you very much sir. I have solved it!

For the other problem try
<?php query_posts("posts_per_page=1&category_name=Headline"); ?>
If that doesn’t work try:
In category_name=Headline is Headline the category slug?
<?php query_posts("posts_per_page=1&category_name=headline"); ?>
if that doesn’t work check what the category slug is.