ffmpeg -i FX-vs-mTw.dk_1map_de_nuke.flv name.avi
FFmpeg version SVN-r0.5.1-4:0.5.1-1ubuntu1, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  configuration: --extra-version=4:0.5.1-1ubuntu1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
  libavutil     49.15. 0 / 49.15. 0
  libavcodec    52.20. 1 / 52.20. 1
  libavformat   52.31. 0 / 52.31. 0
  libavdevice   52. 1. 0 / 52. 1. 0
  libavfilter    0. 4. 0 /  0. 4. 0
  libswscale     0. 7. 1 /  0. 7. 1
  libpostproc   51. 2. 0 / 51. 2. 0
  built on Mar  4 2010 12:35:30, gcc: 4.4.3

Seems stream 0 codec frame rate differs from container frame rate: 50.00 (50/1) -> 25.00 (50/2)
Input #0, flv, from 'FX-vs-mTw.dk_1map_de_nuke.flv':
  Duration: 02:42:18.90, start: 0.040000, bitrate: N/A
    Stream #0.0: Video: h264, yuv420p, 720x576 [PAR 1:1 DAR 5:4], 25 tbr, 1k tbn, 50 tbc
    Stream #0.1: Audio: 0x0000, 0 channels, s16
Output #0, avi, to 'name.avi':
    Stream #0.0: Video: mpeg4, yuv420p, 720x576 [PAR 1:1 DAR 5:4], q=2-31, 200 kb/s, 90k tbn, 25 tbc
    Stream #0.1: Audio: mp2, 0 channels, s16, 64 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1
[mpeg4 @ 0x91ed710]removing common factors from framerate
[mp2 @ 0x91edc60]encoding 0 channel(s) is not allowed in mp2
Error while opening codec for output stream #0.1 - maybe incorrect parameters such as bit_rate, rate, width or height