Blank page / Messed up page

If you have a blank page or a messed up page in the backend or frontend, you can probably make your website to write out the error, if you would open up your wp-config.php file, and put this code right under the <?php part:

error_reporting(E_ALL); ini_set('display_errors',1);

If this is happening in your backend, and this won’t write out the error, you could try to put this code into these files too:
wp-content/plugins/nextend-accordion-menu/admin.php
wp-admin/includes/screen.php
wp-admin/admin.php