I had some experiments and the results are very weird! I copied the same image in a new file...pasted in the same position as the other..If I export jst the image on the stage it looks fine..but If i transform the image on the stage into an MC without changing size, position..it looks jagged in the middle...more weird thing is:
I left the image tranformed into an MC in the same position, then i copy the movieclip and position it under the first, break the MC to the original image, export and both images looks fine! So If i export just the MC it looks like crap, while If i export the crappy MC and the image..they looks fine! I think this is madness...I cant get rid of this stupid problem....I hope Adobe will patch this shittty Flash....