@sodesay, this error appears before you actually start burning, doesn't it? So it is not related to the media you use.
I think it indicates that something is wrong with the structure of the files, which Nero checks. You should see the exact information in the main Nero window. I often see it when a .bup file is different from the .ifo file. You can fix that, or just burn anyway (if this is indeed the error). After all, it is only a +rw so you can use it again.