Yesterday, I used my SONY DVD Rewriter to copy some DVDs, and I used Nero 6's "Copy DVD" option. After copying the first DVD, when I put in the second DVD to again copy it, there is some kind of error at the start and wouldn't copy. But after I reboot my system, everything is fine and I was able to copy the second DVD. Again, Nero encounters some kind of error on copying the third DVD, and after I reboot, it was again normal. Can somebody explain this?