EDIT : Solved 

I've been spinning around for 2 days now so I decided to beg the community for help lol

I'm coding a live username checker and I have a problem with the data returned by my Ajax request.

( http://www.youtube.com/watch?v=9owt8HnO4dI I made a video, sorry it's in french but even without the audio, the video pretty clearly explain itself)

I have three pages :

- registration.php // registration form

- chain_check.php // check for forbidden special characters

- usr_chk.php // check into the database if the username is available

Problem : when the user enters his username, onBlur the function check_name is called and returns if there's a problem (chain_check or usr_chk) but then, if he edits it, the function is called, the response is correct (as I can see with firebug) but it's not updated on the screen and the validation var either (usrnm) :(

Here's my code, it's pretty clean so if you could tell me what's wrong with it, I could go further 

Thanks!!!!

1. // Live check
2. function check_name() {
3.       var username = $("#username").val();
4.             if(username.length > 5) {
5.             $("#availability_status").html('<?php echo $strAvChk; ?>'); // Checking availability...
6.                         jQuery.ajax({
7.                         type: "POST",
8.                         url: '/inc/check_chain.php', // tracking special characters
9.                         data: "u="+ username +"&st=5", 
10.                         global: false, // fixed it!
11.                         cache: false,
12.                         success: function(response) {
13.                                     if(response == 1) { 
14.                                     jQuery.ajax({
15.                                     type: "POST",  
16.                                     url: "/inc/usr_chk.php", // checking database if available
17.                                     data: "u="+ username,
18.                                     cache: false,     
19.                                     success: function(response){  
20.                                                 $("#availability_status").ajaxComplete(function(event, request){
21.                                                 if(response == 1){
22.                                                 usrnm = 0;
23.                                                 $("#availability_status").html('<?php echo $strAvNo; ?>'); // not available
24.                                                 } else {
25.                                                 usrnm = 1;
26.                                                 $("#availability_status").html('<?php echo $strAvOk; ?>'); // available
27.                                                 }
28.                                           }); 
29.                                     }
30.                               });
31.                         } else {
32.                         usrnm = 0;
33.                         $("#availability_status").html('<?php echo $strAvNo; ?>'); // contains forbidden characters
34.                         }
35.                   }
36.             }); 
37.             } else {
38.             usrnm = 0;
39.             $("#availability_status").html('<?php echo $strAvSh; ?>'); // username too short
40.             }
41. }