RangeValidator Not Working When Selecting DropDownList Value Using JQuery?

I inherited a site which I am in the middle of updating which has a DropDownList and a RangeValidator assigned to it. The data is bound to the dropdown on Page_Load. The values are retrieved from the database so the value property of each item is set to the unique ID of the item in the DB.

The RangeValidator looks something like:

<asp:rangevalidator id="ddRangeValidator" runat="server" ControlToValidate="ddMenu" ErrorMessage="Please select value in range" MinimumValue="1" MaximumValue="100000" Type="Integer">*</asp:rangevalidator>

I have a method which automatically populates this value in jQuery e.g.

$("#ddMenu").val("An Option");

This works, however, when I try to post the page the range validation fails. Then even if I manually select that value, or select another valid value it still won't validate. The only way to make it validate is to select non-valid value and then re-selecting a valid one.

Here is the data binding code:

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load, Me.Load

If Not Page.IsPostBack Then
Dim ds As New DataSet()
Dim myDbObject As New myDbObject()
ds = myDbObject.ToDataSet() // retrieves all objects from the database

[Code]....