偶的源码：
        public void bindXml(string xmlUrl)
        {
            System.Xml.XmlDocument doc = new System.Xml.XmlDocument();
            doc.Load( System.AppDomain.CurrentDomain.BaseDirectory+"kkjj.xml");
            //doc.Load(xmlUrl);
            doc.SelectNodes("/rss/channel");
            System.Xml.XmlNode root = doc.DocumentElement;
            System.Xml.XmlNode xn = root.SelectSingleNode("/rss/channel");
            outStr += "相册名称：" + xn.SelectSingleNode("title").InnerText;//相册名称
            outStr += "<br>相册url：" + xn.SelectSingleNode("link").InnerText;//相册url
            outStr += "<br>相册图片：<img src='" + xn.SelectSingleNode("image/url").InnerText + "' />";//相册首页图片

            //outStr += "<br><img src='" + xn.SelectNodes("item")[0].SelectSingleNode("enclosure").Value + "'>";
            System.Xml.XmlNodeList xnl = xn.SelectNodes("item");
            outStr += "<br>相册图片数：" + xnl.Count.ToString() + "张";

            System.Xml.XmlNamespaceManager nsmanager = new System.Xml.XmlNamespaceManager(doc.NameTable);
            nsmanager.AddNamespace("media", "http://search.yahoo.com/mrss/");

            // 创建包含 XPATH 表达式的字符串以进行计算。
            string exprString = String.Format("// {0}:group", "media");

            System.Xml.XmlNodeList nodelist = doc.SelectNodes(exprString, nsmanager);

            outStr += "<br>media:title:"+nodelist[0].SelectSingleNode("media:title",nsmanager).Attributes["type"].InnerText;





//            for(int i=0;i<xnl.Count;i++)
//            {
//                outStr += "<br> <img src='"+xnl[i].SelectSingleNode("enclosure").Attributes["url"].InnerText+"' />";
//            }
        }

当时看到了。。gg的xml里面有冒号，就卡卡解决了。。
付上xml片段

- <media:group>
  <media:title type="plain">02.JPG</media:title> 
  <media:description type="plain" /> 
  <media:keywords /> 
  <media:thumbnail url="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/s72/02.JPG" height="48" width="72" /> 
  <media:thumbnail url="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/s144/02.JPG" height="96" width="144" /> 
  <media:thumbnail url="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/s288/02.JPG" height="192" width="288" /> 
  <media:content url="http://lh3.google.com/pengpengsay/R3C96dqJBUI/AAAAAAAAAEo/j3csPO0ig7o/02.JPG" height="400" width="600" type="image/jpeg" medium="image" /> 
  <media:credit>成刚</media:credit> 
  </media:group>

xml地址：http://picasaweb.google.com/pengpengsay/lNFxFK