Music files Preview stopped working in Finder

I think it happened after upgrade to 10.4.5, but maybe not. I used to be able to listen to the mp3 songs and watch video clips in the Preview column in Finder. I found it very handy. But now the small player is no longer there. The Preview column just shows file information. How can I re-enable this.

Thanks in advance.

In the Preview column does it still have a small triangle just before the word "preview" at the very top of the column?
If so, try pressing the arrow so that it points down.

Oh, how embarrassing! :) Thanks a lot!