Did you make any changes in relating to Codecs? What is the last thing you did before this started?
Easiest way out is to re-insiall MPlayer if you haven't tried already.
Stone walls do not a prison make,
Nor iron bars a cage;
Minds innocent and quiet take
That for an hermitage;
If I have freedom in my love,
And in my soul am free,
Angels alone that soar above
Enjoy such liberty. - Richard Lovelace