When I click on the "confirm order" button in domain insulindedenhaag.nl the result is an error 500 page.
(Only when iDEAL payment is chosen)
I think the problem might have something to do with new certificates I installed for IDEAl payment.
I'm not sure but that is the only change as far as I remember.
After upgrading VM and OPC still the same error occurs.
Latest versions Virtuemart 2.6.28 OPC 2.0.286 Joomla 2.5.28
C.Steijn