Error: Cannot use object of type stdClass as array

i think that's about "buggy" form data, but dff should help me find that and not freak out ;-)

2011-05-02 22:24:46 127.0.0.1 PHP Fatal error: Cannot use object of type stdClass as array in /home/xl/workspace/sanago/sites/all/modules/drupalforfirebug/drupalforfirebug.module on line 484
2011-05-02 22:24:46 127.0.0.1 PHP Stack trace:
2011-05-02 22:24:46 127.0.0.1 PHP 1. {main}() /home/xl/workspace/sanago/index.php:0
2011-05-02 22:24:46 127.0.0.1 PHP 2. menu_execute_active_handler() /home/xl/workspace/sanago/index.php:22
2011-05-02 22:24:46 127.0.0.1 PHP 3. call_user_func_array() /home/xl/workspace/sanago/includes/menu.inc:501
2011-05-02 22:24:46 127.0.0.1 PHP 4. node_page_edit() /home/xl/workspace/sanago/includes/menu.inc:0
2011-05-02 22:24:46 127.0.0.1 PHP 5. drupal_get_form() /home/xl/workspace/sanago/modules/node/node.pages.inc:16
2011-05-02 22:24:46 127.0.0.1 PHP 6. drupal_build_form() /home/xl/workspace/sanago/includes/form.inc:188
2011-05-02 22:24:46 127.0.0.1 PHP 7. drupal_prepare_form() /home/xl/workspace/sanago/includes/form.inc:316
2011-05-02 22:24:46 127.0.0.1 PHP 8. drupal_alter() /home/xl/workspace/sanago/includes/form.inc:1038
2011-05-02 22:24:46 127.0.0.1 PHP 9. drupalforfirebug_form_alter() /home/xl/workspace/sanago/includes/module.inc:1002
2011-05-02 22:24:46 127.0.0.1 PHP 10. drupalforfirebug_array_compare() /home/xl/workspace/sanago/sites/all/modules/drupalforfirebug/drupalforfirebug.module:131
2011-05-02 22:24:46 127.0.0.1 PHP 11. drupalforfirebug_array_compare_code() /home/xl/workspace/sanago/sites/all/modules/drupalforfirebug/drupalforfirebug.module:365
2011-05-02 22:24:46 127.0.0.1 PHP 12. drupalforfirebug_array_compare_code() /home/xl/workspace/sanago/sites/all/modules/drupalforfirebug/drupalforfirebug.module:485
2011-05-02 22:24:46 127.0.0.1 PHP 13. drupalforfirebug_array_compare_code() /home/xl/workspace/sanago/sites/all/modules/drupalforfirebug/drupalforfirebug.module:485