This si a data corruption (most likely the disk has been scrached). I suggest you try to clean the DVD with a soft cloth.
If that dosent work, AND AT THE COST OF TOTALLY DESTROYING THE DVD, you can put it in the oven at 200 C for 15-20 seconds, let it cool down, and then try (if it works, i strongly suggest you make a image of the DVD wiht Daemon tools lite, since the DVD will die soon after it works.
Most times, that error means the dvd is about to become useless from damages.
The Oven *trick* should ONLY be used as a last resort, so if other people have better ideas, i sugegst you try those first. (soft cloth is one of them).
If need more information about the oven trick, whisper me.