weird behaviors for UID

Hi All,
I'm trying to duplicate a node with a function but there is some weird behaviors in UID

function passiva_copia($nid) {
  $node = node_load($nid);
  global $user;

  $newnode = array(
    'uid' => $user->uid,  // <<< here is the problem
    'comment' => 2,
    'promote' => 1,
    'type' => $node->type,
    'status' => $node->status,

    'idanag' => $node->idanag,
    ......
  );

  drupal_set_message($newnode->uid . " - " . $user->uid );

drupal_set_message return " 0 - 1 "

So it seems that

$newnode = array(
    'uid' => $user->uid,

doesn't' work,

My user is UID 1 and I don't have any idea why $user->uid return the correct UID but is not passed to $newnode

is it a bug of 6.x

could someone help please?

thanks in advance

luca