Due to legal restrictions, a default installation of Ubuntu does not play DVDs out of the box

(not even with 10.4 jaunty jackalope).

The problem is that most DVD come encrypted with the CSS2 standard, whichs codec is missing.

Inserting and watching a DVD simply does not work. 

I would have loved a more informative error message from the system instead of simply not

playing it - but I guessed that it would be some codec/legal restriction problem.

I found a working solution here

http://maketecheasier.com/how-to-watch-dvd-in-ubuntu-gutsy/2008/03/14

although step 1 (installing ubuntu-restricted-extras) was optional for me. Just try to execute

 "sudo /usr/share/doc/libdvdread3/install-css.sh"

if it does not work, install the restricted extras before:

"sudo apt-get install ubuntu-restricted-extras"

and try it again. this should do it. worked perfectly for me!