Most of times this problem is caused by a bad burned disc, and most of times the culprit is a low quality disc. Too bad, in the market only a single brand of DL discs proved to be reliable: Verbatim. All other brands have a quality widely variable from ugly to crappy :doh:
The only solution is trying to recover all files trying to read the disc with as many drives as possible until you can recover all data, and then burn again on a good quality disc.
It can be helpful to add some parity data to the disc next time. I use DVDisaster for this