Error message CAPTCHA session reuse attack detected.

duplicate of #1395184: Forms with AJAX trigger "CAPTCHA session reuse attack detected." error

This question,I have solved, but my method isn't a very good way,because my client don't allow me to alter this captcha module, so i have to alter my custom my module,you can reference my method:

1---------:1st

//  my this function name is ---------: custom_init
function yourmodulename_init() {
  if(isset($_POST['captcha_sid'])){
	$posted_captcha_sid = $_POST['captcha_sid'];
    $expected_captcha_token = db_query(
    "SELECT token FROM {captcha_sessions} WHERE csid = :csid",
       array(':csid' => $posted_captcha_sid)
    )->fetchField();
	$_POST['captcha_token'] = $expected_captcha_token;
	$_POST['debug_captcha_token'] = $expected_captcha_token;
  }
}

2--------:2ed:

//  my this function name is ---------: user_login_custom_validate
function yourform_validate($form, &$form_state){
	if(isset($_POST['captcha_sid'])){
		$posted_captcha_sid = $_POST['captcha_sid'];
		$expected_captcha_token = $_POST['debug_captcha_token'];
		$token_ret = db_update('captcha_sessions') 
		->fields(array(
		  'token' => $expected_captcha_token,
		))
		->condition('csid', $posted_captcha_sid, '=')
		->execute();
	}
}

I use 7.x.1.0-beta2 but I have warning
CAPTCHA session reuse attack detected after uploading file

=====
Here the problem

file 1 upload
CAPTCHA session reuse attack detected
file2 upload

I don't know how to fix it.Comment #2 is not clear to me as a beginner.

I am sorry, forgot to attach

I have found the discussion here
http://drupal.org/node/918856

although applying patch captcha-patch-10022012.patch is not clean
but I don't have any problem with "CAPTCHA session reuse attack detected"

Duplicate of #918856: CAPTCHA Session Reuse message on webforms .