I think I have got it up and running now and it was NOT a software problem. The box started to behave normally (no crashes, no hanging with spinning dots) when I moved the tuner card from slot B to slot A (I only have one card) on mu VU+ Duo2 box. I would not have figured it out without some extra debugging. I now run OpenPli 6 RC and when I mounted the harddrive from my old (and broken) DM 800 HD SE, it even restored the backup from the drive so I'm a happy camper now. But I will still talk to the vendor who was the one mounting the tuner in slot B; it cost me a couple of hours of troubleshooting.
Thank you for your help.