Exporting PNG Sequence

I am trying to export my animation as a PNG sequence. I have my animation as a movie clip on the main timelime. When I File> Export Movie > PNG Sequence , I get a sequence of PNGs of the same frame.

This shows that Movie Clip is not being played when I export as PNG Sequence. I need the Movie Clip as on the main timeline because, I am manipulating it as an instance.

I intend to use transparency feature of PNG to later manipulate in After Effects 7.

Thanks in advance.

I got it to work. http://forums.awn.com/archive/index.php/t-3778.html

I just needed to change the behaviour of the movie clip to graphic and set it to loop.