store bought dvd's will not play only dvd-rs will work

when trying to play a store bought dbd I get the message "Could not read DVD. This may be because the DVD is encrypted and a DVD decryption library is not installed."
AS an extreme newb to linux I have no idea how to remedy this.
I am running edubyntu 11.10 if that helps

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: libgstreamer0.10-0 0.10.35-1
ProcVersionSignature: Ubuntu 3.0.0-14.23-generic 3.0.9
Uname: Linux 3.0.0-14-generic i686
ApportVersion: 1.23-0ubuntu4
Architecture: i386
Date: Sat Jan 14 11:57:45 2012
ExecutablePath: /usr/bin/totem
InstallationMedia: Edubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gstreamer0.10
UpgradeStatus: No upgrade log present (probably fresh install)