It's most likely media problem. I'd insist on trying another media brand before you proceed.These are Ritek 4x DVD-R disks (with ritek printing, not ridata or arita). One of my friends could use these successfully for many recordings, thats why I thought they should work. My friend has an LG 4081 writer. Also, the plextor media compatibility page said that there are supported Ritek 4x DVD-R disks, but I'm not sure that this is the type they tested.
Neither of this exclude possibility that it's a media problem of some kind. Poor support by *your* unit firmware (is it latest?), bad batch or even counterfeit media (e.g. Maxell brand was exposed to counterfeit attempt)...
I'll try some other DVD-Rs too, but currently I don't have any.Since then I also tryed DVD+R disks and they work well, I also have rewriteable disks of both + and - kind and can use them too.
All this (as well as weird errors during DAO attempt) speaks in favor of particular media problem. A.