FUNimation recently blogged about a production error with the third Dragon Ball Z season set (the orange bricks from several years back), where the second disc is accidentally pressed with the content from the fifth disc. Only those who have purchased a copy of the set from its latest production batch within the last month or so may be subject to this error, but if you have any issues, they are offering a replacement version. Check out their blog entry for all the full details.
Needless to say, we encourage all of our readers to abandon these flawed sets and instead invest in the Dragon Box releases!