this wont efect you at all if your are using paypal pro. it will effect you if you are using Paypal Standard.
if you use paypal standard, you will need to update the WA_eCart/WA_eCart_Definition_PHP.php file, and change:
$header = "POST /cgi-bin/webscr HTTP/1.0\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
to:
$header = "POST /cgi-bin/webscr HTTP/1.1\r\n";
$header .= "Content-Type: application/x-www-form-urlencoded\r\n";
$header .= "Host: www.paypal.com\r\n";