NullReferenceException was unhandled

Question

Hi could somebody please help me with this as i have been trying to fix it for hours!!!
I keep receving the "NullReferenceException was unhandled " message in the line in bold

public static Conditions GetCurrentConditions(string location)
{
Conditions c;
c = null;
c = new Conditions();

c.GetCurrentConditions();

XmlDocument xmlConditions = new XmlDocument();
xmlConditions.Load(string.Format("http://www.google.com/ig/api?weather={0}", location));
if (xmlConditions.SelectSingleNode("xml_api_reply/weather/problem_cause") != null)
{
c = null;
}
else
{
Conditions cond = new Conditions();
cond.Town = xmlConditions.SelectSingleNode("/xml_api_reply/weather/forecast_information/city").Attributes["data"].InnerText;
cond.Condition = xmlConditions.SelectSingleNode("/xml_api_reply/weather/current_conditions/condition").Attributes["data"].InnerText;
cond.TempC = xmlConditions.SelectSingleNode("/xml_api_reply/weather/current_conditions/temp_c").Attributes["data"].InnerText;
cond.TempF = xmlConditions.SelectSingleNode("/xml_api_reply/weather/current_conditions/temp_f").Attributes["data"].InnerText;
cond.Humidity = xmlConditions.SelectSingleNode("/xml_api_reply/weather/current_conditions/humidity").Attributes["data"].InnerText;
cond.Wind = xmlConditions.SelectSingleNode("/xml_api_reply/weather/current_conditions/wind_condition").Attributes["data"].InnerText;

}

return c;
}

Answer 1

first of all there is an error
  if (startTime < endTime)
                {
                    richTextRxMessage.Text = richTextRxMessage + Convert.ToString(elapsedTime);
                }
it needs to be:
      richTextRxMessage.Text = richTextRxMessage.Text + Convert.ToString(elapsedTime);