get_permalink returning wrong link in excerpt

Are you using a child theme?

No, i created my own theme.
But i used the twenty-ten as basis

The first months it worked fine.
My problem: I dont now what caused the “function-crash”

How are you calling this function?

Do u mean in my Template?

I use this code:
<?php the_excerpt(); ?>

And the continue_reading button is created by the function twentyten_continue_reading_link() in my function.php

the continue_reading button is created by the function twentyten_continue_reading_link() in my function.php

How? I see no add_hook or add_filter in the code you posted above.

There never has been a filter.

This is the code of the original Twenty-Ten Theme:

/**
 * Returns a "Continue Reading" link for excerpts
 *
 * @since Twenty Ten 1.0
 * @return string "Continue Reading" link
 */
function twentyten_continue_reading_link() {
	return ' <a href="'. get_permalink() . '">' . __( 'Continue reading <span class="meta-nav">&rarr;</span>', 'twentyten' ) . '</a>';
}

That’s because it is called using a second function:

function twentyten_auto_excerpt_more( $more ) {
	return ' …' . twentyten_continue_reading_link();
}
add_filter( 'excerpt_more', 'twentyten_auto_excerpt_more' );

I also use this function!

the permalink returns the current page’s permalink and not the excerpt’s permalink.

are you using a page template?

if yes, what is the full code of that template?

This is the Code of the Page:

<?php
	/**
	 * Template Name: Home-2
	 * A custom page template forthe Home-2-Page.
	 */
get_header(); ?>

<div id="content">
 <?php if ( have_posts() ) while ( have_posts() ) : the_post(); ?>
  <div id="intro-text-home">
   <?php the_content(); ?>
   <?php endwhile; ?>
  </div>
  <!--intro-text-->
 <div id="blog-intro-home"><!--blog-header-->
  <div id="blog-article-home">
    <?php $args = array( 'numberposts' => 1, 'order'=> 'DESC', 'orderby' => 'post_date' ); $postslist = get_posts( $args ); foreach ($postslist as $post) :  setup_postdata($post); ?>
    <h2 class="entry-title"><a href="<?php the_permalink(); ?>" title="<?php printf( esc_attr__( 'Permalink to %s', 'twentyten' ), the_title_attribute( 'echo=0' ) ); ?>" rel="bookmark"><?php the_title(); ?></a></h2>
    <?php the_date('d', '<span class="day">', '</span>'); ?>
    <span class="month"><?php the_time('M'); ?></span>
    <span class="author">gepostet von <?php the_author(); ?></span>
    <br />
    <a href="<?php the_permalink(); ?>"><?php the_post_thumbnail (thumbnail); ?></a>
    <br /><br />
    <?php the_excerpt(); ?>
  </div>
  <!--blog-article-->
 </div>
 <!--blog-intro-->

<?php endforeach; ?>

<?php get_footer(); ?> 

</div>
<!--end content-->

you could try:

<a href="<?php echo get_permalink($post->ID); ?>">..........

It doesnt work!

It is so weird: every permalink above the <?php the_excerpt(); ?> works fine, but if i put the permalink below the <?php the_excerpt(); ?> it doesnt work!!

the permalink returns the current page’s permalink

do your excerpts have a ‘read-more’ link at the end?
i.e. does your theme have any filters for instance on ‘excerpt_more’ ?