Server side grouping resets form values

[Jamy]

I am using 2 DateTimePickers and a submit button in my form.

Outside of my form I am server side binding a grid. When changing dates and posting back the data is returned to the grid as expected and the dates stay as is for the DateTimePickers.

The problem is when I use grouping... as soon as I do, the postback causes the dates to come in as nulls to my action and my default date range is used and the dateTimePickers are returned empty.

Is this a bug in the grouping or am I doing something wrong?

<%  using (Html.BeginForm()){ %>

    <fieldset>
        <legend>Search By</legend>

        <% Html.Telerik().DateTimePicker()
               .Name("dtpStart")
               .Format("M/d/yyyy h:mm tt")

               .Render(); %>



        <% Html.Telerik().DateTimePicker()
               .Name("dtpEnd")
               .Format("M/d/yyyy h:mm tt")
               .Render(); %>



        <input type="submit" value="Search" class="t-button t-state-default" style="display:inline-block" />
    </fieldset>


<%} %>

<% Html.Telerik().Grid(Model).Name("Grid1").Columns(columns =>
{
    columns.Template(c =>

public ActionResult Search(DateTime? dtpStart, DateTime? dtpEnd)
{
    ViewData["dtpStart"] = dtpStart;
    ViewData["dtpEnd"] = dtpEnd;
    DateTime d = new DateTime(1900,1,1,0,0,0);

    if (!dtpStart.HasValue || !dtpEnd.HasValue)
    {
        dtpStart = new DateTime(2009, 10, 27, 0, 0, 0);
        dtpEnd = new DateTime(2009, 10, 27, 4, 30, 0);
    }
    int startStamp = (int)dtpStart.Value.Subtract(d).TotalMinutes;
    int endStamp = (int)dtpEnd.Value.Subtract(d).TotalMinutes;

    decimal disconnectThreshold = 0;