[xubuntu-users] Can't play a DVD iso file but the DVD plays fine

[MR ZenWiz]

I have Xubuntu 12.04.2 with all the updates and I'm having an odd problem.

I routinely make iso copies of any DVDs I buy, usually with k3b or
l9copy, depending on which one will actually copy the disc.

I tried watching one today, Star Trek XI (the last one before the one
that's now in the theaters) and I had a fascinating experience.

When I tried to watch the movie through the ISO file, VLC, mplayer and
Parole all failed to play the movie either properly or at all.  But
when I put the DVD in one of my writers, it played just fine.

I've pulled down all the plugins for gstreamer and I have libdvdread
4.2.0 installed, but the iso playback, if you can call it that, was
blotchy, out of sync and slow, and unwatchable.

What am I missing?

Thanks.

MR