Access control disappeared

Somehow did the Access control disappear. I changed the code for now to

$form["Access Control"] = array(
'#type' => 'fieldset',
'#title' => t("Access Control"),
'#description' => t('No Access Controls to add for this forum'),
'#attributes' => null,
'#collapsible' => TRUE,
'#collapsed' => FALSE,

And at least I can see it again now. Does somebody know why Access control disappeared in the first place?

Regards