It may... if you proved FTP access I can debug it and get it fixed for you.
If you add this to the failure page it would give you the log with information about the exact error:
<?php
@session_start();
var_dump($_SESSION);
?>
My guess it is a math issue of some sort (%tax or something) that causes more than two decimals to be sent to paypal. That can be easily fixed, but I'll need to confirm that is the issue and get access to your files to fix it.