Re: Sony DSC-H50 Memory Card
Welcome to the site, jasp!
You have a very interesting problem and I think you've annswered your own question. I can't see how your Mark 2 Duo card could be a problem. But it appears that you have the proof that it is. To make absolutely sure you should format the problem card in the camera and try again. If it still does the same thing, then try another Mark 2 Duo card. If a second card gives you the same result then you know the problem is definitely related to the card type and not just your memory card.