I found the mistake, thats weired.
I use PRTG Network Grapher 7 for hardware monitoring over interent/lan and it uses WPI interface and SNMP to monitor hardware things like drive allocation, cpu, ram and so on. I had my local excluded from this monitoring and switched it back on just yesterday because I had to watch my temp drive when I'm on work to react on low space.
After I excluded my computer some minutes ago and started burning another DVD, everything went smooth again. I thought it couldn't be and enabled my computer again, burned a DVD and there was the error again. I disabled and burned another one, everything went fine.
It must have to do with the WPI counters that where pooled by the PRTG Probe Service.
And BTW: There was never ever a firmware update for my H66N, I don't know why, maybe because it was released as S-ATA device just some weeks before they released their BlueRay devices.