My client reported this problem to me, after debugging, i saw:
modules\paypal\controllers\front\expresscheckout.php ln: 473
Tools::redirectLink($this->context->link->getPageLink('order-confirmation', true, '&id_cart='.$cart->id.'&id_module='.$this->module->id.'&key='.$customer->secure_key));
And the actual method is:
public function getPageLink($controller, $ssl = null, $idLang = null, $request = null, $requestUrlEncode = false, $idShop = null, $relativeProtocol = false)
So the third parameter is wrong. If i fix it, and put null as third parameter, it works.