ActionScript 1/2 :: Variables Sent By Post Dependent On Browser Type / Version?

I am writing a type of mail form in AS2 of Flash CS4. I collect two variables (nameCli and messageCli) I setup a "sending button" to appear only when there is a minimum of characters (2) under nameCli AND a minimum of 10 characters in messageCli. When that button is pressed I POST these two vars tru email_lv to email2.php. I do this check to be absolutely sure that these vars have contents.

It works and tests well on several computers (PCs) under XP, Vista and 7.
I haven't tested on a Mac
Under IE and Firefox 3.0.xx
I get the email with the correct values.

The problem: somehow, now and then I get (and worse, my client, to whom I wrote this app, gets) an "empty" email. That is, the subject of these emails are: "Request from" and blank. No name. The message is also blank. Since I know, with no doubt that these vars have content, otherwise the send button wouldn't come up, I am puzzled. I have no idea of what OS or Browsers these users have. Would be possible that some browsers would "block" the vars sent via POST?

email_lv.sendAndLoad("email2.php",dummy_lv, "POST");
email2.php is:
<?php
$to = 'any@whomever.com';$to2 = 'another@whomever.com';
$subject= 'Request from ' . $_POST["nameCli"];
$message = $_POST["messageCli"];
$headers = 'From: WebSite@clientserver.com'. "
" . 'Reply-To: doNOTreply@clientserver.com'. "
" . 'X-M ailer: PHP/'.phpversion() ." ";
mail($to, $subject, $message, $headers);mail($to2, $subject, $message, $headers);
?>