javascript - PageMethod failure over 90% of the time -

i have webmethod:

    /// <summary>     /// check if user name 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;         }     } 

that called in .js

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'; } 

}

with web.config

<configuration> <system.web>   <compilation debug="true" targetframework="4.0" />   <httpruntime executiontimeout="3600" maxrequestlength="2147483647" /> </system.web></configuration> 

the problem i'm getting 90% of time, return in onerror, when debug data, in webmethod function go ok.

this error:

error on server method 'loguser' ; stack trace; status code: 0; exeption type:; timed out: false 

some 1 have idea can causing this?