[jQuery] JQUERY .POST PROBLEM

[wattsup]

I am having some problems with a jquery script that I am writing. The
problem is after I receive the data from the php file jquery seems to
skip the if statement.  I am logging to console and it is showing yes/
no depends on email address. I am enclosing my scripts in case someone
can help me.


<script src="javascripts/jquery-1.2.6.js" type="text/javascript"
charset="utf-8"></script>
<script src="javascripts/jquery.validate.js" type="text/javascript"
charset="utf-8"></script>
<script src="javascripts/jquery.corner.js" type="text/javascript"
charset="utf-8"></script>
<script src="javascripts/jquery.lightbox.packed.js" type="text/
javascript"></script>

$(document).ready(function(){
        $("#email").blur(function(){
                var post_string = $(this).val();

                $("#msgbox").removeClass().addClass('messagebox').text
('Checking...').fadeIn(1000);
                        $.post("php/email.php",{ email_check: post_string} 
,function(data){
                                console.log(data); // show data value in console
                                 if(data=='no') {  // email not avaiable
<------------------------- Skipping this area
                                        $("#msgbox").fadeTo(200,0.1,function(){
                                                $(this).html('email address 
already exists').addClass
('messageboxerror').fadeTo(900,1)
                                        });
                                } else { // email avaiable
<-------------------------- Always gos here no matter what
                                        $("#msgbox").fadeTo(200,0.1,function(){
                                                $(this).html('email available 
to register').addClass
('messageboxok').fadeTo(900,1);
                                        });
                                } // end if
                        }); // end post
        }); // end email blur
}); // end doc ready




PHP FILE

if(isset($_POST['email_check'])) {
        $email = $_POST['email_check'];

        require_once('config.inc.php');
        require(MYSQL);

        $result = @mysql_query("SELECT * FROM members WHERE (user_email =
'$email')");
        $row_num = mysql_num_rows($result);

        if( $row_num > 0){
                // "unavailable to register";
                $valid = "no";
        }else{
                // "available to register";
                $valid = "yes";
        };

        echo $valid;
        mysql_close();
}


I have been working on this all day and can not figure out why the
data is skipping the if statement. if you have any ideals please let
me know.