DVD+RW data backup problem - some files not copied correctly.

I have a Dell Dimension 4600 just a few months old.  I have been trying to back up data files (MP3 and WMA) to the DVD+RW drive using Roxio DataDVD.  I set up the project with the files to be copied, then when I run the copy to DVD, everything appears to work correctly.  But then when I reload the DVD and start looking at the individual files, sometimes I find several files have 0 length.  When I right-click on these files, I get no drop-down menu.  If I try to drag the file name from the DVD to my desktop. I get error message, "Cannot copy - the file or directory is corrupted and unreadable."  The corrupted files seem to be full folders; i.e. all the files in a folder either copy correctly or get corrupted.  But sometimes all files appear okay - it seems to be a function of which files I am copying, or the number of folders, or such.  I have done 2 updates to the Roxio software, first from Dell updates, then a later update I found on Roxio site, and I have done the firmware Flash update to the NEC 1100A drive, and I still have the same problem.  This has happened with multiple discs,.

With the HP CD drive and software I had on my previous PC, the CD writer had a verify option so I could at least trust it had written correctly if I got no error messages.  If I hadn't taken a close look at lost of my files, I could have have easily missed the errors and figured I had good backups, when actually they are corrupted.

Has anyone else run into this?  Any suggestions other than call Dell?