[NuAlpha]

In the file "include/register.php", directly below...

$smarty->assign("error",$error);

...there should be:

if (@include('validate_zipcode.php')) {
	$b_zipcode = validate_zipcode($b_zipcode,$b_country);
	if (!empty($s_zipcode))
		$s_zipcode = validate_zipcode($s_zipcode,$s_country);
	else $s_zipcode = $b_zipcode;
}

Remove the "@" symbol before the "include" and then register a test customer to see if some problem shows up in your code. Note that PHP must be set to show errors for this to work.