Please help!! dvd movie keeps stopping....?

i borrowed gladiator from my local store, and im trying to play it on my laptop. it worked fine for the first 56 mins of the mive, but at 56 mins nero said "the disc could not be read. (im using the new nero played, but this also happens with windows media player, except in wmp it jsut closes without any messages) anyways after the message i close the video, reopen it and go to scene selector, and go to the scene after the point where it stops playing (e.g if it stops in the middle of scene 2 then i go to scene 3) and then the movie works normally again, untill it reaches another point nd same thing happens again, and again i have to choose the next scene and miss some parts of the movie. does anyone know why this happens? i have tried cleaning the disc but no solution...