Ubuntu Multimedia :: DVDs Stop Playing About Halfway Through

I've got this weird problem where my DVDs - just standard netflix DVDs mostly - will stop playing about halfway through. At first I thought it was a problem with the disks, but it has happened far too often now, and I tested one of the disk and it played fine in Windows - though I had to sit through 20 minutes of unskippable ads to check.

I get exactly the same problem regardless of player; I usually use VLC, but VLC, MPlayer, and at least one other all stop in exactly the same place. There's no buffering or freezing or anything, it just stops as if it were the end of the disk, and it always stops at the same time on a disk (not always at the same time on different disks). I can't skip past that point, it's like there is nothing past that point.