Problem when selecting in a combobox

[feanor91]

Hello

I have a combobox, when I click to select a value, I choose one, but the value is not updated into the combobox text part (see picture of the process) :
first I click to expand : ok
second, and third I chosee, the combo collapsed, nothing appeared in the text part
fourth, I click elsewhere an the value selected apear.

Here the combo definition. I see nothing strange in it.

<ext:ComboBox ID="ComboBox1"
    runat="server"
    Editable="false"
    Enabled="True" 
    DisplayField="STR_CountryName"
    ValueField="INT_idCountry" 
    EmptyText="Please choose a value">
    <Store>
        <ext:Store ID="Store3" runat="server">
            <Proxy>
                <ext:HttpProxy Url="jsonDAL/ReturnJsonCountry.aspx" Json="false" Timeout="3000">
                </ext:HttpProxy>
            </Proxy>
            <Reader>
                <ext:JsonReader>
                    <Fields>
                        <ext:RecordField Name="INT_idCountry"  Type="Int"/>
                        <ext:RecordField Name="STR_CountryName" Type="String" />
                    </Fields>
                </ext:JsonReader>
            </Reader>
        </ext:Store>
    </Store>
    <Listeners>
        <Expand Handler="#{ComboBox1}.store.reload();"/>
    </Listeners>
</ext:ComboBox>

The combobox defined below works well :

<ext:ComboBox ID="ComboBox3"
    runat="server"
    Editable="false"
    Enabled="True" 
    DisplayField="STR_NameWorldRegion"
    ValueField="INT_idWorldRegion" 
    EmptyText="Please choose a value">
    <Store>
        <ext:Store ID="Store1" runat="server">
            <Proxy>
                <ext:HttpProxy Url="jsonDAL/ReturnJsonWorldRegion.aspx" Json="false" Timeout="3000">
                </ext:HttpProxy>
            </Proxy>
            <Reader>
                <ext:JsonReader>
                    <Fields>
                        <ext:RecordField Name="INT_idWorldRegion"  Type="Int"/>
                        <ext:RecordField Name="STR_NameWorldRegion" Type="String" />
                    </Fields>
                </ext:JsonReader>
            </Reader>
        </ext:Store>
    </Store>
    <Listeners>
        <Expand Handler="#{ComboBox3}.store.reload();"/>
    </Listeners>
</ext:ComboBox>