Samsung - if these packages are not installed on your MD (but they are installed on your core) then you will not be able to playback encrypted/commerical DVDs, DVD rip images or media files that use the win32 codecs (such as WMV, WMA, and many AVI containers that contain similar codecs - you can't tell just by looking at an AVI what codec it uses) but you would be able to playback those files on your core... so you should look at that first.
Don't forget, just because you have installed these packages on your core doesn't mean they are on your MDs. You have to execute the same commands on the MDs too. You can do this, like this...
on your core:
sudo -s (hit enter, then supply your password)
ssh moon## (where ## is your MD device number)
sudo apt-get install w32codecs libdvdcss2