Unable to databind to CheckBoxList (but no problems with RadioButtonList)

 I'm unable to databind values from db to CheckBoxList-control (inside ModalPopUp-control):
 .ASPX:
<asp:CheckBoxList ID="myCheckBoxList" runat="server" />
.ASPX.CS
private void BindCheckBoxList()

{
myCheckBoxList.DataSource = db.GetItems();
myCheckBoxList.DataValueField = "ID";
myCheckBoxList.DataTextField = "Text";
myCheckBoxList.DataBind();
}
Nothing is displayed. However when I change the very same code to use RadioButtonList, everything works perfectly (this is inside ModalPopUp-control too):

.ASPX:
<asp:RadioButtonList ID="myRadioButtonList" runat="server" />
.ASPX.CS
private void BindRadioButtonList()


{
myRadioButtonList.DataSource = db.GetItems();

myRadioButtonList.DataValueField = "ID";

myRadioButtonList.DataTextField = "Text";

my ...