Can't use Post in Google Contact API

Question

I'm trying Google Contact API from oAuth Playground. I post data

<atom:entry xmlns:atom="http://www.w3.org/2005/Atom" xmlns:gd="http://schemas.google.com/g/2005"&gt;
  <atom:category scheme="http://schemas.google.com/g/2005#kind"
    term="http://schemas.google.com/contact/2008#group"/&gt;
  <atom:title type="text">Salsa group</atom:title>
  <gd:extendedProperty name="more info about the group">
    <info>Nice people.</info>
  </gd:extendedProperty>
</atom:entry>

Can't finished and return is here

POST /m8/feeds/groups/[email protected]/full/ HTTP/1.1
Host: www.google.com
Pragma: no-cache
Accept: */*
Authorization: OAuth oauth_version="1.0", oauth_nonce="aa2c6cb5a97698882d7bd9f6e75a6a30", oauth_timestamp="1265782718", oauth_consumer_key="www.mysteryzillion.org", oauth_token="1%2Fk1BCc9XN9oDb2Vat7Vpp7Q", oauth_signature_method="HMAC-SHA1", oauth_signature="M0hqGEGrI9m4zgVtUTKhJPTIDJM%3D"
Content-Type: application/atom+xml
GData-Version: 2.0
Content-Length: 408

<pre><atom:entry xmlns:atom="\"http://www.w3.org/2005/Atom\"" xmlns:gd="\"http://schemas.google.com/g/2005\""&gt;
  <atom:category scheme="\"http://schemas.google.com/g/2005#kind\"" term="\"http://schemas.google.com/contact/2008#group\""&gt;&lt;/atom:category&gt;
  <atom:title type="\"text\"">Salsa group</atom:title>
  <gd:extendedproperty name="\"more" info="" about="" the="" group\="">
    <info>Nice people.</info>
  </gd:extendedproperty>
</atom:entry>HTTP/1.1 400 Bad Request
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Date: Wed, 10 Feb 2010 06:18:38 GMT
Expires: Wed, 10 Feb 2010 06:18:38 GMT
Cache-Control: private, max-age=0
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
Server: GFE/2.0
X-XSS-Protection: 0

Open quote is expected for attribute "{1}" associated with an  element type  "xmlns:atom".</pre>

I am try this feed uri

http://www.google.com/m8/feeds/groups/default/full/