hook_node_access called more than once
$node contains all the content-type in your application as value. So, you need to set your node access based on the $node value.

function hook_node_access($node, $op, $account) {
  $type = is_string($node) ? $node : $node-&gt;type;
  if($type == 'forum') {
    //set your permission based on $op value.
  }
}