Hi,
I faced this problem.
Found the next: http://www.joomlahackers.net/virtuemart-tutorials/virtuemart-duplicate-orders.html (http://www.joomlahackers.net/virtuemart-tutorials/virtuemart-duplicate-orders.html)
I hope it will help someone solving the problem in the new version.
Drukman.
Ehrm, your link is pointing to a Virtuemart 1 fix ! VM 1 is obsolete.