DVD ISO copy weirdness

[夜神 岩男]

I bought a new movie on DVD the other day for my kid (Christmas and 
all...). I wanted to back it up because I've noticed a few of my older 
DVDs don't play correctly anymore (blocky in spots or don't play period 
but are studio cuts that used to work!).

Normally I just put a DVD in the drive, select "Copy disk..." and move 
through the dialogue to save it to an .iso. Later I can either have the 
computer or the player play it from anywhere in the house.

Simple.

But today this one is acting strangely. It is giving me a css key error, 
which is weird, because this is not BlueRay or anything, and it works 
just fine in the ancient for-TV DVD player, so its nothing new.

Beyond that, I can open the disk up and see the typical DVD directories: 
{VIDEO,AUDIO}_TS

Looking in VIDEO_TS to see what's the matter, everything can be played 
just fine. No CSS problems. The DVD works in Media Player, VLC, etc. 
just fine. I can run each individual chapter segment as well. But the 
total size of VIDEO_TS claims to be 46GB, about 10 times bigger than it 
should be... and I'm not going to copy 46GB just to get a movie. It was 
a good movie, but not THAT good.

Any ideas?