Update gone wrong, error on top of the page, HELP

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘_show_post_preview’ was given in /home/marthamari/domains/devrijezangvogel.nl/public_html/wp-includes/plugin.php on line 406

This is the error I see on the top of the page

I can login at the backend but I can’t open the update page.

At the bottom is a fatal error: Fatal error: Call to undefined function has_post_format() in /home/marthamari/domains/devrijezangvogel.nl/public_html/wp-content/themes/pinboard/slider.php on line 10

Hope you can help!