Execution of authentication request returned unexpected result: 404

[Mudassir]

Dear all
i was using
Google.GData.An alytics
and
Google.GData.Cl ient
to retrieve some google analytics report in my web application and the code was as follows

            string username = "abc@gmail.com";
            string password = "myPasswordHere";
            string profileId = "ga:88376970";
            string _from = Convert.ToDateTime(dtpFrom.SelectedDate.Value.ToString()).ToString("yyyy-MM-dd");
           string _to = Convert.ToDateTime(dtpTo.SelectedDate.Value.ToString()).ToString("yyyy-MM-dd");
            AccountQuery AccountsQuery = new AccountQuery();
            service = new AnalyticsService("DoogalAnalytics");
            service.setUserCredentials(username, password);
try
            {
                DataFeedUrl = "https://www.google.com/analytics/feeds/data";
                DataQuery PageViewQuery = new DataQuery(DataFeedUrl)
                {
                    Ids = profileId ,
                    Metrics = "ga:pageviews",
                    Dimensions = "ga:date",
                    Sort = "ga:date",
                    GAStartDate = _from,
                    GAEndDate = _to
                };
                StringBuilder strData = new StringBuilder();
                int maxValue = 0;
                int today = 0;
                List<int> gList = new List<int>();                
                foreach (DataEntry entry in service.Query(PageViewQuery).Entries)
                {
                    var value = entry.Metrics.First().IntegerValue;
                    gList.Add(value);
                    maxValue = value > maxValue ? value : maxValue;
                    today = entry.Metrics.Last().IntegerValue;
                    strData.AppendFormat("{0},", value);
                }
               
            }
            catch (Exception ex)
            {
                Response.Write(ex.Message.ToString());
            }

This code was working perfectly fine util 5 days back and i have been using this code for the last 7 or 8 months, but now suddenly i am facing the error "Execution of authentication request returned unexpected result: 404".
When i searched google.
I have searched alot but could not find any solution.
Any help or guidance will be greatly appreciated.

Regards:
Mudassir