I use Totem xine.
I add the medibuntu repositories from a terminal:
sudo wget http://www.medibuntu.org/sources.list.d/intrepid.list --output-document=/etc/apt/sources.list.d/medibuntu.list press enter
sudo apt-get update && sudo apt-get install medibuntu-keyring && sudo apt-get update press enter
I close the terminal.
I open up Synaptic Package Manager.
I install totem xine and remove totem gstreamer.
I install ubuntu-restricted-extras.
I install libdvdcss2(for dvd playback)
I reboot just in case.
And bingo. I open up totem and all my media plays without a hitch(except cds which I use RhythmBox and karaoke which I use PyKaraoke).
If that doesn't work do a fresh install and start again.