internal server error due to paypal standard change action

http://forum.civicrm.org/index.php/topic,7836.0.html

While i was looking for the solution and i posted it on paypal forums i learnt that when we are sending values to paypal, action should be https://www.paypal.com/cgi-bin/webscr

But when i debug CiviCRM Code i found this 3 lines where action is www.paypal.com/xclick
File :-- CRM/Core/Payment/PayPalImp.php (line 403)

$url = $this->_paymentProcessor['url_site'];
$sub = empty( $params['is_recur'] ) ? 'xclick' : 'subscriptions';
$paypalURL = "{$url}{$sub}?$uri";

Even i replaced xlick => cgi-bin/websrc and it worked but i m still confused and not sure when that error will occur. Am i on right track .

Note:-- whenever i got a error its containing xclick. so replacing xclick with cgi-bin/websrc is the soluction ?

Here is the link to my post on paypal

http://developer.paypal-portal.com/pdn/board/message?board.id=basicpayments&message.id=37323

Even I checked UberCart Code what url they are using for paypal payment and i found there they have used the action https://www.paypal.com/cgi-bin/webscr for paypal processor.

Any Small Help Would Be Appreciated

Thanx in Advance

-Altaf