PageMethod失败超过90％的时间

Question

我有一个这个WebMethod：

    /// <summary>
    /// Check if a User Name is valid
    /// </summary>
    /// <param name="UserName"></param>
    /// <param name="UserPassword"></param>
    /// <returns></returns>
    [WebMethod]
    public static Object LogUser(String UserName, String UserPassword)
    {
        try
        {
            return new BLL.LogIn().LogUser(UserName, UserPassword);
        }
        catch
        {
            return false;
        }
    }

在这个.js中调用

function LogUser() {

var UserName = document.getElementById('txt_usr').value;
var UserPassword = document.getElementById('txt_pass').value;


// Validations
if (UserName == "")
{
    alert("Falta informar el nombre del Usuario");
    return;
}

if (UserPassword == "") {
    alert("Falta informar el password del Usuario");
    return;
}

PageMethods.LogUser(UserName, UserPassword, onSucess, onError);

function onSucess(result) {
    if (result == false) {
        alert("El Usuario o Contraseña incorrecto");
    }
    else
    {
        alert("true");
        windows.location.href = 'List.aspx';
    }
    alert('Sucess');
}
function onError(error) {
    alert("Error: " + error.get_message() + "; " +
    "Stack Trace: " + error.get_stackTrace() + "; " +
    "Status Code: " + error.get_statusCode() + "; " +
    "Exception Type: " + error.get_exceptionType() + "; " +
    "Timed Out: " + error.get_timedOut());
    windows.location.href = 'errorManipulation.aspx';
}

}

使用此Web.Config

<configuration>
<system.web>
  <compilation debug="true" targetFramework="4.0" />
  <httpRuntime executionTimeout="3600" maxRequestLength="2147483647" />
</system.web></configuration>

我得到的问题是90％的时间，返回得到OnError，但是当我调试数据时，在WebMethod中该函数就可以了。

这是错误：

Error on the server method 'logUser' ; Stack Trace; Status Code: 0; Exeption Type:; Timed Out: false

有人知道可能导致这种情况的原因吗？