Conversions to WMV stutter sporadically - ffmpeg SVN-r7856
Attached is a file named "ed.avi" that illustrates this problem well.

Files converted to the WMV container "stutter" in Windows Media Player for Windows and the Flip4Mac WMV QuickTime components for Mac OS X, and cause playback/conversion warnings in libavcodec-based software.
When affected frames are reached by WMP or Flip4Mac, playback of new frames is halted until the next keyframe.

Example command (log file - wmvstutter.txt):
ffmpeg -i ed.avi -vcodec wmv2 -b 900k -g 48 -an baded.wmv

Resulting file (baded.wmv) stutters at the following second marks:
6
9
10
14
16
24
25
50

When baded.wmv is converted through ffmpeg back to an .AVI, there is one of these errors for every stutter:
[wmv2 @ 0x3cc694]concealing 220 DC, 220 AC, 220 MV errors
The video at each point continues conversion, with noticeable errors until the next keyframe.

Example command (log file - wmvstutterplayback.txt):
ffmpeg -i baded.wmv -b 900k -g 48 -an badedplayback.avi

FFmpeg version SVN-r7856, Copyright (c) 2000-2006 Fabrice Bellard, et al.
  configuration: 
  libavutil version: 49.3.0
  libavcodec version: 51.32.0
  libavformat version: 51.8.0
  built on Feb  6 2007 15:21:48, gcc: 4.0.1 (Apple Computer, Inc. build 5367)
Input #0, avi, from 'ed.avi':
  Duration: 00:00:51.9, start: 0.000000, bitrate: 420 kb/s
  Stream #0.0: Video: mpeg4, yuv420p, 320x176, 30.00 fps(r)
  Stream #0.1: Audio: mp3, 32000 Hz, stereo, 128 kb/s
Output #0, asf, to 'baded.wmv':
  Stream #0.0: Video: wmv2, yuv420p, 320x176, q=2-31, 900 kb/s, 30.00 fps(c)
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
frame=  396 q=2.0 size=     754kB time=13.2 bitrate= 467.7kbits/s    
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
frame=  841 q=2.0 size=    1579kB time=28.0 bitrate= 461.3kbits/s    
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
frame= 1251 q=2.0 size=    2372kB time=41.7 bitrate= 466.0kbits/s    
[wmv2 @ 0x3cc694]warning, clipping 1 dct coefficients to -255..255
frame= 1559 q=2.0 Lsize=       0kB time=52.0 bitrate=   0.1kbits/s    
video:2933kB audio:0kB global headers:0kB muxing overhead -99.985714%