[SOLVED] System.DirectoryServices.DirectoryServicesCOMException: An operations error occurred

I have the same web app working in three others servers. Anyone have any idea why is not working in the 4th server? See the error and stacktrace:

An operations error occurred.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details:
System.DirectoryServices.DirectoryServicesCOMException: An operations error occurred.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[DirectoryServicesCOMException (0x80072020): An operations error occurred. ] System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail) +454 System.DirectoryServices.DirectoryEntry.Bind() +36 System.DirectoryServices.DirectoryEntry.get_AdsObject() +31 System.DirectoryServices.PropertyValueCollection.PopulateList() +22
System.DirectoryServices.PropertyValueCollection..ctor(DirectoryEntry entry, String propertyName) +96
System.DirectoryServices.PropertyCollection.get_Item(String propertyName) +142 System.DirectoryServices.AccountManagement.PrincipalContext.DoLDAPDirectoryInitNoContainer() +1134 System.DirectoryServices.AccountManagement.PrincipalContext.DoDomainInit() +37 System.DirectoryServices.AccountManagement.PrincipalContext.Initialize() +124 System.DirectoryServices.AccountManagement.PrincipalContext.get_QueryCtx() +31 System.DirectoryServices.AccountManagement.Principal.FindByIdentityWithTypeHelper(PrincipalContext context, Type principalType, Nullable'1 identityType, String identityValue, DateTime refDate) +14
System.DirectoryServices.AccountManagement.Principal.FindByIdentityWithType(PrincipalContext context, Type principalType, String identityValue) +73
System.DirectoryServices.AccountManagement.UserPrincipal.FindByIdentity(PrincipalContext context, String identityValue) +25
Infraero.TINE3.STTEnterprise.Web.Common.Seguranca.ServicoAutenticacao.EfetuarLogin(AcessoUsuario acessoUsuario, String senha) in D:\SVN\STT\trunk\4-0_CodigoFonte_Enterprise\4-4_SRC\Infraero.TINE3.STTEnterprise.Web\Common\Seguranca\ServicoAutenticacao.cs:34 Infraero.TINE3.STTEnterprise.Web.Controllers.LoginController.ValidarUsuarioAD(String matricula, String senha, AcessoUsuario acessoUsuario) in D:\SVN\STT\trunk\4-0_CodigoFonte_Enterprise\4-4_SRC\Infraero.TINE3.STTEnterprise.Web\Controllers\LoginController.cs:92 Infraero.TINE3.STTEnterprise.Web.Controllers.LoginController.ValidarUsuario(String matricula, String senha) in D:\SVN\STT\trunk\4-0_CodigoFonte_Enterprise\4-4_SRC\Infraero.TINE3.STTEnterprise.Web\Controllers\LoginController.cs:80 Infraero.TINE3.STTEnterprise.Web.Controllers.LoginController.Index(LoginViewModel loginViewModel) in D:\SVN\STT\trunk\4-0_CodigoFonte_Enterprise\4-4_SRC\Infraero.TINE3.STTEnterprise.Web\Controllers\LoginController.cs:54 lambda_method(Closure , ControllerBase , Object[] ) +108
System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +17
System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary'2 parameters) +208
System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary'2 parameters) +27
System.Web.Mvc.<>c__DisplayClass15.b__12() +55 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func'1 continuation) +263
System.Web.Mvc.<>c__DisplayClass17.b__14() +19 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList'1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +191
System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +343
System.Web.Mvc.Controller.ExecuteCore() +116
System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +97 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10
System.Web.Mvc.<>c__DisplayClassb.b__5() +37
System.Web.Mvc.Async.<>c__DisplayClass1.b__0() +21
System.Web.Mvc.Async.<>c__DisplayClass8'1.b__7(IAsyncResult _) +12 System.Web.Mvc.Async.WrappedAsyncResult'1.End() +62 System.Web.Mvc.<>c__DisplayClasse.b__d() +50
System.Web.Mvc.SecurityUtil.b__0(Action f) +7 System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60
System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8963149 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184

EfetuarLogin Method:

public static bool EfetuarLogin(User user, string password)
{
    bool isValid = false;

    if (user != null)
    {
        PrincipalContext context = new PrincipalContext(ContextType.Domain);

        using (context)
        {
            isValid = context.ValidateCredentials(user.Login, password);

            if (isValid)
            {
                UserPrincipal userAD = UserPrincipal.FindByIdentity(context, user.Login);

                MySession.CurrentUser = new MyUserSession()
                {
                    Id = user.Id,
                    ProfileId = user.ProfileId ,
                    Login = user.Login ,
                    Name = userAD.Name
                };
            }
        }
    }

    return isValid;
}