weird dvd burning issue

[nny]

I have a 64 rig with a nec 2500. i've been backing up some dvds with dvdshrink/nero and they work perfectly, even on my xbox which can be picky about burned media. then i went home and built my brother a similar comp with the nec 2500, installed the same software and burned a couple dvds. when i got back home i realized the dvds i burned from his comp dont work in the xbox and have read errors on my comp, yet they worked on his comp. does anybody know what happened?