[theora] Is it a Bug ?

[mesecam]

Good Evening,

I've encoded a 00:41:56 (hh:mm:ss) long video using 2 passes.

Software : ffmpeg2theora.exe
md5sum: 5dae7693db8be158e8cb5374048e3a5e


The bit-rate seems to dramatically drop at around 00:40:00. The end of
the video is really ugly.
See pictures here:

http://dl.free.fr/v2D8Y2vfu ~ 2 megs


command line:
ffmpeg2theora -x 720 -y 400 -V 1075 --noaudio --aspect 16:9 -K 240
--optimize --soft-target --first-pass theora2pass.log -o test.ogv
my_file.avi

Am i doing anything wrong?