Basic authentication not working in IE or Chrome when live

GET http://xxxx.xxxx.com/api/values HTTP/1.1
Host: xxxx.xxxxx.com
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:26.0) Gecko/20100101 Firefox/26.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: __utma=160871039.470048631.1389004711.1389004711.1389004711.1; __utmc=160871039; __utmz=160871039.1389004711.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)
Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=
Connection: keep-alive

GET http://#####.######.com/api/values HTTP/1.1
Accept: text/html, application/xhtml+xml, */*
Accept-Language: en-GB
User-Agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0; MDDCJS)
Accept-Encoding: gzip, deflate
Host: ####.#####.com
Cookie: __utma=160871039.1791605041.1363174995.1374568675.1374856696.5; __utmz=160871039.1363174996.1.2.utmcsr=bing|utmccn=(organic)|utmcmd=organic|utmctr=######; __qca=P0-637394059-1363174995765
Connection: Keep-Alive
Authorization: Negotiate TlRMTVNTUAABAAAAl4II4gAAAAAAAAAAAAAAAAAAAAAGAvAjAAAADw==
DNT: 1

public class BasicAuthenticationMessageHandler : DelegatingHandler
    {
        private const string BasicAuthResponseHeader = "WWW-Authenticate";
        private const string BasicAuthResponseHeaderValue = "Basic";

        public IProvidePrincipal PrincipalProvider { get; set; }

        protected override System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken)
        {
            AuthenticationHeaderValue authValue = request.Headers.Authorization;
            if (authValue != null && !String.IsNullOrWhiteSpace(authValue.Parameter))
            {
                Credentials parsedCredentials = ParseAuthorizationHeader(authValue.Parameter);
                if (parsedCredentials != null)
                {
                    Thread.CurrentPrincipal = PrincipalProvider
                        .CreatePrincipal(parsedCredentials.Username, parsedCredentials.Password);
                }
            }
            return base.SendAsync(request, cancellationToken)
                .ContinueWith(task =>
                {
                    var response = task.Result;
                    if (response.StatusCode == HttpStatusCode.Unauthorized
                        && !response.Headers.Contains(BasicAuthResponseHeader))
                    {
                        response.Headers.Add(BasicAuthResponseHeader
                                             , BasicAuthResponseHeaderValue);
                    }
                    return response;
                });
        }

        private Credentials ParseAuthorizationHeader(string authHeader)
        {
            string[] credentials = Encoding.ASCII.GetString(Convert
                                                                .FromBase64String(authHeader))
                .Split(
                    new[] { ':' });
            if (credentials.Length != 2 || string.IsNullOrEmpty(credentials[0])
                || string.IsNullOrEmpty(credentials[1])) return null;
            return new Credentials()
            {
                Username = credentials[0],
                Password = credentials[1],
            };
        }
}