totals of the cart item amounts do not match order amounts

My client got this error the totals of the cart item amounts do not match order amounts. I am new to Opencart & Paypal. I have tried this extension module http://www.opencart.com/index.php?route ... n_id=16699

I have changed five lines in catalog/model/payment/pp_express.php

Changed line number 261

$item_total = number_format($item_total + $item_price, 2);

to

$item_total = number_format($item_total + $item_price, 2, '.', '');

Changed line number 180

$item_total += number_format($item_price * $item['quantity'], 2);

to

$item_total += number_format($item_price * $item['quantity'], 2, '.', '');

Changed line number 187

$data['L_PAYMENTREQUEST_0_ITEMWEIGHTVALUE' . $i] = number_format($weight / $item['quantity'], 2);

to

$data['L_PAYMENTREQUEST_0_ITEMWEIGHTVALUE' . $i] = number_format($weight / $item['quantity'], 2, '.', '');


Changed line number 267

$data['PAYMENTREQUEST_0_ITEMAMT'] = number_format($item_total, 2);

to

$data['PAYMENTREQUEST_0_ITEMAMT'] = number_format($item_total, 2, '.', '');


Changed line number 268

$data['PAYMENTREQUEST_0_AMT'] = number_format($item_total, 2);

to

$data['PAYMENTREQUEST_0_AMT'] = number_format($item_total, 2, '.', '');


But, still I got the same error The totals of the cart item amounts do not match order amounts