Thanks for the reply Joerg, it is a public server and I'm not going
through any proxies so it is strange, its also strange that it only
happens randomly but quiet frequently, around 50% of the time, some
sample code that calls the page in question is

       [STAThread]
       public static void Main() {
           string url = "http://site.sports.betfair.com/menu/
LoadMenuNodesAction.do?
sReturnPath=parent.frames['menu']&method=getMenuEvents&menuNodeId=11589568&strArrayName=allSkeletonArray&iParentID=11589568&layerName=allMarketsTreeContainer&strMenuPathArrayName=allPathArray&menuPathLayer=menuParents1&locale=en_GB";
           for(int i = 0 ; i < 10 ; i++) {
               HttpWebRequest hwr = (HttpWebRequest)
HttpWebRequest.Create(url);
               try {
                   using(WebResponse wr = hwr.GetResponse()) {
                       using(Stream s = wr.GetResponseStream()) {
                           using(StreamReader sr = new
StreamReader(s)) {
                               Console.WriteLine(sr.ReadToEnd());
                           }
                       }
                   }
               } catch(WebException we) {
                   Console.WriteLine(we.ToString());
               }
               Console.ReadLine();
           }
       }

Running a packet sniffer I can see that the correct text is been
returned but I'm not sure if it is been chunked correctly, its also
strange that the url works 100% in IE.

Thanks for any help, if you dont have time to look at it further dont
worry about it, usuing 1.0 is an acceptable alternative as its a call
that is only used occasionaly, I'm more just curious than anything
else.

Joe.