problem with mediaPlayback slider

[giomod]

Hi everybody,
I'm working on a project in which users can display several streaming videos loaded dinamically (flv using Media Server 2).

I decided to use mediaPlayback component to display those videos on the stage and everything works fine but the playback slider has a strange behaviour:

when I try to drag the cursor along the bar it only moves to the beginning of the bar and the video re-start from the beginning.
Also the elapsed time counter returns the value "NN:NN:NN:NN".
That is, I cannot decide where to move the playHead.

Is there someone who can explain me this strange behaviour?
Do I have to initialize the mediaPlayback first?
If it is so, how can I do?



thanks a lot