getJSON Function Not Entered - Not Working

getJSON Function Not Entered - Not Working

The GetCats function is called. However, when it return, the getJSON function is never entered. I have tried several ways. Am I doing something wrong, or is my JsonResult invalid?

Thanks.

From Controller Class:
       public JsonResult GetCats()
        {
            // enters and returns fine
            List<ListItem> list = new List<ListItem>() {   
              new ListItem() { Value = "1", Text = "VA" },   
             new ListItem() { Value = "2", Text = "MD" },   
              new ListItem() { Value = "3", Text = "DC" }   
         };

            return this.Json(list);
        }

From HTML Page:
      $.getJSON('/Category/GetCats', null, function (data) {
            // alert never reached
            alert("hi");
        });