RadioButtonList SelectedIndexChanged fires only once

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ASP.NET

RadioButtonList SelectedIndexChanged is firing only for the first time & not next time.I am unable to understand why it is happening.Plz help me.
Below is the code used.

 protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
    {
       if (isAlive)
       {
        rbllive.SelectedIndex = 0;
       }
       else
       {
       rbllive.SelectedIndex = 1;
       }
   }
}

protected void rbllive_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (rbllive.SelectedIndex == 1)
            {
                pnllive.Visible = true;

            }
            else
            {
                pnllive.Visible = false;

            }
        }

[edit]Edited for more readible code block - losmac[/edit]