Ubuntu Multimedia :: FFmpeg Symbol Lookup Error After Possible Update

I noticed that a lot of software updates were ready today so I installed all of them without thinking to make a note of what they were, so I don't know if ffmpeg or one of its dependencies was amongst them. The very next time I ran ffmpeg, it gave me an error I haven't seen before. After downloading a file from BBC's iPlayer site using get-iplayer, I ran a script to convert it to a format suitable for my Samsung YP-Q2 personal media player. I copied the command out of that script and pasted it onto the command line so that I could capture the console output of that encoding session, shown below:

Code:
[garry tv]$ ffmpeg -i inputfile.mp4 -acodec libmp3lame -ar 44100 -ab 128k -ac 2 -vcodec mpeg4 -b 1024k -r 15 -s qvga outputfile.avi
FFmpeg version git-bcf9828, Copyright (c) 2000-2009 Fabrice Bellard, et al.
built on Oct 25 2009 11:48:38 with gcc 4.4.1
Configuration: --enable-gpl --enable-nonfree --enable-shared --enable-pthreads --enable-libx264 --enable-libfaac --enable-libtheora
libavutil 50. 3. 0 / 50. 3. 0
libavcodec 52.37. 1 / 52.20. 0
libavformat 52.39. 2 / 52.31. 0
libavdevice 52. 2. 0 / 52. 1. 0
libswscale 0. 7. 1 / 0. 7. 1
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x9d27700]ISO: File Type Major Brand: isom
st:1 removing common factor 48 from timebase

Seems stream 0 codec frame rate differs from container frame rate: 100.00 (100/1) -> 25.00 (25/1)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'inputfile.mp4':
Duration: 00:58:39.02, start: 0.000000, bitrate: 831 kb/s
Stream #0.0(und), 1/50: Video: h264, yuv420p, 640x360, 1/100, 25 tbr, 50 tbn, 100 tbc
Stream #0.1(und), 1/1000: Audio: aac, 48000 Hz, stereo, s16
ffmpeg: symbol lookup error: ffmpeg: undefined symbol: avcodec_channel_layout_num_channels
[garry tv]$

This error, "undefined symbol" is what makes me think that either ffmpeg or one of its dependencies has been updated or the error would have occurred before now. I've been using the script with the command in the above form for some weeks now with no problems, almost always converting an MP4 (but sometimes a .mov) into an AVI. Thinking that it might be the version of ffmpeg in the standard repos, I followed the advice of this thread and removed the standard ffmpeg and installed the one from Medibuntu. (Removing the standard one took WinFF and DVDRip with it, but I reinstalled those afterwards, and I'm sure they don't come into the equation otherwise.) I re-ran the command and the error was exactly as before. Is ffmpeg recently borked or am I missing something obvious? Or something obscure, for that matter?