I had the same problem with NERO. I believe it is related to +R versus -R DVDs. I tried to burn about 20 +R DVDs and NERO always said it worked but the DVDs were blank.
I then switched back the the -R DVDs and have sucessfully burned 6 DVDs.
I am using a laptop with Windows Vista and the latest NERO 220.127.116.11 but had the problem with the prevous “d” version too. I did not discover if the +R / -R situation was solved for that version using the -R DVDs.