When trying to update an entry on Google Apps No ETag found is returned.. Adding entries works just fine, but can't neither update or delete entries!?

The ETag is added to the header in one of the last lines in the code:

$this->gdata->updateEntry($doc->saveXML(), $update_entry->getEditLink()->href, null, array('If-Match' => '*'));

Exception

Expected response code 200, got 409

Code

private function update_entry($data, $update_entry=null){
        $doc = new DOMDocument();
        $doc->formatOutput = true;

        $entry = $doc->createElement('atom:entry');
        $entry->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:atom', 'http://www.w3.org/2005/Atom');
        $entry->setAttributeNS('http://www.w3.org/2000/xmlns/', 'xmlns:gd', 'http://schemas.google.com/g/2005');
        $doc->appendChild($entry);

        if($update_entry){
            preg_match('/^"?([^"]*)"?$/i', $update_entry->getEtag(), $matches);
            $etag_value = $matches[1];

            $entry->setAttribute('gd:etag', $etag_value);
            $id = $doc->createElement('id', 'http://www.google.com/m8/feeds/contacts/'.$this->admin_user.'/base/'.$data['alias']);
        $entry->appendChild($id);
        }

        $name = $doc->createElement('gd:name');
        $entry->appendChild($name);
        $fullName = $doc->createElement('gd:fullName', $data['name']);
        $name->appendChild($fullName);

        if($data['title']){
            $org = $doc->createElement('gd:organization');
            $org->setAttribute('rel' ,'http://schemas.google.com/g/2005#work');
            $entry->appendChild($org);
            $orgName = $doc->createElement('gd:orgTitle', $data['title']);
            $org->appendChild($orgName);
        }

        if($data['email']){
            $email = $doc->createElement('gd:email');
            $email->setAttribute('address', $data['email']);
            $email->setAttribute('rel', 'http://schemas.google.com/g/2005#work');
            $entry->appendChild($email);
        }

        if($data['phone_work']){
            $phone_work = $doc->createElement('gd:phoneNumber', $data['phone_work']);
            $phone_work->setAttribute('rel', 'http://schemas.google.com/g/2005#work');
            $entry->appendChild($phone_work);
        }

        if($data['phone_work_mobile']){
            $phone_work_mobile = $doc->createElement('gd:phoneNumber', $data['phone_work_mobile']);
            $phone_work_mobile->setAttribute('rel', 'http://schemas.google.com/g/2005#work_mobile');
            $entry->appendChild($phone_work_mobile);
        }

        if($update_entry){
            echo $doc->saveXML();
            $this->gdata->updateEntry($doc->saveXML(), $update_entry->getEditLink()->href, null, array('If-Match' => $etag_value));
        }
        else{
            $this->gdata->insertEntry($doc->saveXML(), 'http://www.google.com/m8/feeds/contacts/'.self::DOMAIN.'/full');
        }
    }

XML

<?xml version="1.0"?>
<atom:entry xmlns:atom="http://www.w3.org/2005/Atom" xmlns:gd="http://schemas.google.com/g/2005" gd:etag="CxFbERtcFit7I2Bu">
  <id>http://www.google.com/m8/feeds/contacts/admin_user@domain.com/base/alias</id>
  <gd:name>
    <gd:fullName>name</gd:fullName>
  </gd:name>
  <gd:organization rel="http://schemas.google.com/g/2005#work">
    <gd:orgTitle>title</gd:orgTitle>
  </gd:organization>
  <gd:email address="mail@domain.com" rel="http://schemas.google.com/g/2005#work"/>
  <gd:phoneNumber rel="http://schemas.google.com/g/2005#work">22260435</gd:phoneNumber>
  <gd:phoneNumber rel="http://schemas.google.com/g/2005#work_mobile">1112223</gd:phoneNumber>
</atom:entry>