Ajax success data empty on second try?

On click of the form-submit button, an ajax-request will be sent to a php-handler. Well, the request ist sent as it should, I even get my answr from the php-file, but, after getting "The text has to be between 50 and 5000 characters." once, the next time I click my submit butten, the ajax succes() data will stay empty. Why?

AJAX:

<script>
    $("#formID").submit(function(){
        $.ajax({
            url: $(this).attr('action'),
            type: $(this).attr('method'),
            data: $(this).serialize(),
            beforeSend:function(){
                $('#sendBox').html('<div class="loading"><img src="ajax-loader.gif" alt="Loading..." /></div>');
            },
            success: function(data)
            {
                $("#sendBox").html(data);
                $("#sendBox").show('slow');
                if(data.substr(0,8) == "(Contact)"){
                    document.getElementById("formID").reset();
                }
            }
        });
        return false;
    });
</script>

This is my php-handler:

if(strlen($_POST["fName"]) < 3 || strlen($_POST["fName"]) > 30){
        return LangText("Der Name muss zwischen 3 und 30 Zeichen sein.", "Le nom doit étre entre 3 ét 30 charactéres.", "The name has to be between 3 and 30 characters.");
    }else if (!filter_var($fMail, FILTER_VALIDATE_EMAIL)) {
        return LangText("Die E-Mail Adresse ist nicht richtig.", "Votre adresse électronique n´est pas valide", "Your email adress is not valid");
    }else if(strlen($_POST["fText"]) < 50 || strlen($_POST["fText"]) > 5000){
        return LangText("Der Text muss zwischen 50 und 5000 Zeichen sein.", "Le text doit étre entre 50 ét 5000 charactéres.", "The text has to be between 50 and 5000 characters.");
    }else {
//send email
 echo LangText("(Contact) Vielen Dank, sie haben uns kontaktiert.", " (Contact) Merci beaucoup, vous nous avez contacté.", "(Contact) Thank you, your email has been sent.");
}