Thank you.
May be it is the way to go. It is especially good when we have stereo sound which poser does not take.

arfarfarf,
you are right. When I turned off alpha channel, the above problem disappeared.
Probably Poser5 messes up the alpha channels.

Twisted_Symmetry,
unfortunatly, it seems that the problem belongs to poser5.

Anyway, thanks to you guys, now I know how to avoid the problem.
I am happy.

Thanks again.
HimiCo.