LinuxQuestions.org - Package not available, but is referred to by another package.?

I'm not actually sure what this means

but does it mean my Ubuntu sources dont have all the files they should?
I can install some things but nothing related to MAD or DVD work spitting out the below message

Code:

sudo apt-get install mplayer

Reading package lists... Done

Building dependency tree... Done

Package mplayer is not available, but is referred to by another package.

This may mean that the package is missing, has been obsoleted, or

is only available from another source

E: Package mplayer has no installation candidate

Code:

deb http://kubuntu.org/packages/amarok-latest/ dapper main

deb http://security.ubuntu.com/ubuntu/ dapper-security universe

deb http://au.archive.ubuntu.com/ubuntu/ dapper universe

deb-src http://security.ubuntu.com/ubuntu/ dapper-security universe

deb-src http://au.archive.ubuntu.com/ubuntu/ dapper universe

deb http://security.ubuntu.com/ubuntu/ dapper-security main

deb-src http://security.ubuntu.com/ubuntu/ dapper-security main

deb-src http://au.archive.ubuntu.com/ubuntu/ dapper-backports main 

deb http://au.archive.ubuntu.com/ubuntu/ dapper-backports main restricted universe multiverse

deb-src http://au.archive.ubuntu.com/ubuntu/ dapper-updates main 

deb-src http://au.archive.ubuntu.com/ubuntu/ dapper main restricted

deb http://au.archive.ubuntu.com/ubuntu/ dapper-updates main restricted

deb http://au.archive.ubuntu.com/ubuntu/ dapper main restricted

My System Settings
Athlon 64 X2
Kubuntu x86-64
K8-SMP kernel
2.6.15-26-amd64-k8 #1 SMP PREEMPT