@Carraway and @Mateo227
the problem is on both side
for exact encoding in wmv/flv/mp4 format with mencoder you must use the "-of lavf -lavfopts i_certify_that_my_video_stream_does_not_use_b_frames " option
and i haven't used this options..
update to this build
http://www.64k.it/andres/data/a/AutoMen10.exe
the lavfopts is used in both flv and wmv encoding
thanks!
BHH