$ ffmpeg -i 175.wmv -acodec mp3 -ab 56 -f flv -s 320x240 -ar 22050 -g 100 -qscale 9 -aspect 4:3 -me full -flags trell+mv4 -mbd 2 -y test.flv
FFmpeg version SVN-r7760, Copyright (c) 2000-2006 Fabrice Bellard, et al.
  configuration:  --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib --enable-vorbis --enable-libogg --enable-shared --enable-faad --enable-faadbin --enable-faac --enable-a52 --enable-mp3lame --enable-xvid --enable-gpl --enable-amr_nb --enable-amr_wb --enable-memalign-hack 
  libavutil version: 49.2.0
  libavcodec version: 51.29.0
  libavformat version: 51.8.0
  built on Jan 29 2007 16:40:49, gcc: 3.4.2 [FreeBSD] 20040728
[wmv3 @ 0x284b3048]Extra data: 8 bits left, value: 0

Seems stream 1 codec frame rate differs from container frame rate: 1000.00 (1000/1) -> 20.00 (20/1)
Input #0, asf, from '175.wmv':
  Duration: 00:02:07.6, start: 3.000000, bitrate: 385 kb/s
  Stream #0.0: Audio: 0x0162, 48000 Hz, stereo, 384 kb/s
  Stream #0.1: Video: wmv3, yuv420p, 320x240, 20.00 fps(r)
Output #0, flv, to 'test.flv':
  Stream #0.0: Video: flv (hq), yuv420p, 320x240, q=2-31, 200 kb/s, 20.00 fps(c)
  Stream #0.1: Audio: mp3, 22050 Hz, stereo, 56 kb/s
Stream mapping:
  Stream #0.1 -> #0.0
  Stream #0.0 -> #0.1
Unsupported codec (id=0) for input stream #0.0



$ ffmpeg -formats | grep wmv
FFmpeg version SVN-r7760, Copyright (c) 2000-2006 Fabrice Bellard, et al.
  configuration:  --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib --enable-vorbis --enable-libogg --enable-shared --enable-faad --enable-faadbin --enable-faac --enable-a52 --enable-mp3lame --enable-xvid --enable-gpl --enable-amr_nb --enable-amr_wb --enable-memalign-hack 
  libavutil version: 49.2.0
  libavcodec version: 51.29.0
  libavformat version: 51.8.0
  built on Jan 29 2007 16:40:49, gcc: 3.4.2 [FreeBSD] 20040728
 DEVSD  wmv1
 DEVSD  wmv2
 D V    wmv3