To pay the bounty when the bug is resolved you effectively make a donation to Ardour and let Paul/las know about the bounty being resolved and the donation.
That being said, I would think it would be interesting, for grins and giggles, to put in a live CD like AV Linux temporarily, and see if your export has the same behavior when opened up from Ardour rc3 in AV Linux(No need to install AV Linux though you may need to install rc3 in AV Linux when you boot it up). I am referring to the export process here, for the record. But it would help to determine if it is something wonky with your system setup or not (Not prove conclusively unless it eliminated the problem, but help)