Validators doesn't allow to open RadWindow containing insert form

[Harlem98]

Hello.

I'm using CommandItem built in Insert button to open a window with a form to insert new values.

      <telerik:RadWindow ID="UserListDialog" runat="server" Title="Atualizar listagem" Height="400px" OnClientClose="OnClientCloseHandler" 
                            Width="800px" Left="150px" ReloadOnShow="true" ShowContentDuringLoad="false" DestroyOnClose="true"
                            Modal="true" 
                            Behaviors="Close,Move,Resize" CssClass="opaque"  KeepInScreenBounds="True"  >
                            
                                <ContentTemplate>
                                      <uc1:ViewEmissaoTimeSheetEdit ID="EditTimesheet" runat="server"  />
                                </ContentTemplate>
                            
                        </telerik:RadWindow>

            <CommandItemTemplate>
                                     <telerik:RadButton CommandName="InitInsert" RenderMode="Lightweight" ID="AddNewRecordButton" Text="Adicionar nova versão" ToolTip="Adicionar versão"
                                          runat="server" style="background:none; border:none; color:green;">
                                         <Icon PrimaryIconCssClass="rbAdd"></Icon>
                                     </telerik:RadButton>

The problem is, when i use Validators in my form atributtes, the form doesn't open when clicking the insert button.

Validators structure in my form (contained in a user control)

 <telerik:RadTextBox ID="txtAssinaturaTimesheet" runat="server" MaxLength="30"  Width="220px">
                                    </telerik:RadTextBox>
 <%-- <asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server" ControlToValidate="txtAssinaturaTimesheet" Display="Static" 
CssClass="ValidationFont" Text="Campo Obrigatório!" Font-Size="Medium" ></asp:RequiredFieldValidator> --%>

It is a common issue? How can i overcome it?