Here is a quick fix for this issue:
HTML Code:
--- a/skin/common_files/modules/One_Page_Checkout/ajax.checkout.js
+++ b/skin/common_files/modules/One_Page_Checkout/ajax.checkout.js
@@ -441,7 +441,7 @@ ajax.widgets.checkout.obj.prototype.selectShipping = function(elm) {
action: 'update'
},
success: function(a, b, c, d) {
- return s.callback(true, a, b, c, d) && (s.isXPCPayment(paymentid) ? true : s.enableCheckout());
+ return s.callback(true, a, b, c, d) && s.enableCheckout();
},
error: function(a, b, c, d) {
return s.callback(false, a, b, c, d) && s.enableCheckout();