Json: Returning List of Objects In Ajax call 500 error

Json: Returning List of Objects In Ajax call 500 error

I'm having trouble with an ajax call. When I try to pass a string in it works, but when I try to pass a list of objects in it does not work? I tried debugging and the list is definitely populated. But when I try running it with a list I keep getting a 500 (Internal Server Error)? Any suggestions would be very much appreciated!!

Ajax Call:
$(function () {
    $('input[type=checkbox]').change(
     function () {
         if (this.checked) {
             $.post("/Authentication/GetProfiles", {}, function (profiles) {
                alert("success")
               
             });
         }
     });
});


controller:
public ActionResult GetProfiles()
            {
                ProfileManager pm = new ProfileManager(@"Data Source=.\sqlexpress;Initial Catalog='Profiles';Integrated Security=True");
                var profiles = pm.GetProfiles();
                return Json(profiles);

            }