We think the problem lies in these js files:
skin\frontend\default\redriver\js\[url removed, login to view]
app\code\local\Digg\Checkout\controllers\[url removed, login to view]
the former developer gave us this - apparently non-working - advice:
in \skin\frontend\default\redriver\js\[url removed, login to view] you should comment line #843 and enable #842 ===> var params = 'payment[method]=quickpay_standard';
in file \app\code\local\Digg\Checkout\controllers\[url removed, login to view] => comment line #103 and enable #104 -----$redirectUrl = Mage::getUrl('quickpay/standard/redirect');
but these changes didnt solve problem. Please help us fix it.