My recorder has been acting that way for a while. I can do a one shot recording to DVD-R and finalise, but if I try to add to it they whole disk often fails. DVD-RW work fine, they play in other players around the house and in our computers, so I don't buy the non-rewritable ones anymore...
You can finalise DVD-RWs, but I've yet to figure out why you would want to!
