ffmpeg vysync drop complete error

#
# Input is two .flv movies, each of which may have missing video frames.
# Output is a merged .mp4 (side-by-side).
#

ffmpeg -v info -y \
 -i http://jdolan.dyndns.org/tmp/jay_and_gonzo.flv \
 -i http://jdolan.dyndns.org/tmp/jay.flv -filter_complex "
  [0:0] pad='max(240,iw):max(180,ih):0:0', scale='240:180', pad='480:180:240:0' [left];
  [1:0] pad='max(240,iw):max(180,ih):0:0', scale='240:180' [right];
  [left] [right] overlay [out0];
  [0:1] [1:1] amerge [out1]" \
 -codec:a libfaac -ar 44100 \
 -codec:v libx264 -preset medium -vsync drop \
 -map [out0] -map [out1] out.mp4
ffmpeg version 1.1.git-716dbc7 Copyright (c) 2000-2013 the FFmpeg developers
  built on Jun  8 2013 15:27:14 with Apple clang version 3.1 (tags/Apple/clang-318.0.61) (based on LLVM 3.1svn)
  configuration: --prefix=/opt/local --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-libtheora --enable-libschroedinger --enable-libopenjpeg --enable-libmodplug --enable-libvpx --enable-libspeex --enable-libfreetype --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/clang --arch=x86_64 --enable-yasm --enable-gpl --enable-postproc --enable-libx264 --enable-libxvid --enable-nonfree --enable-libfaac
  libavutil      52. 34.100 / 52. 34.100
  libavcodec     55. 12.102 / 55. 12.102
  libavformat    55.  8.102 / 55.  8.102
  libavdevice    55.  2.100 / 55.  2.100
  libavfilter     3. 73.100 /  3. 73.100
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
Input #0, flv, from 'http://jdolan.dyndns.org/tmp/jay_and_gonzo.flv':
  Metadata:
    creationdate    : Mon Jun 10 14:44:12
  Duration: 00:00:19.45, start: 0.000000, bitrate: 312 kb/s
    Stream #0:0: Video: flv1, yuv420p, 320x240, 1k tbr, 1k tbn, 1k tbc
    Stream #0:1: Audio: nellymoser, 22050 Hz, mono, flt
Input #1, flv, from 'http://jdolan.dyndns.org/tmp/jay.flv':
  Metadata:
    creationdate    : Mon Jun 10 14:44:12
  Duration: 00:00:19.38, start: 0.000000, bitrate: 422 kb/s
    Stream #1:0: Video: flv1, yuv420p, 320x240, 1k tbr, 1k tbn, 1k tbc
    Stream #1:1: Audio: nellymoser, 22050 Hz, mono, flt
[Parsed_amerge_6 @ 0x7fa789c1a560] No channel layout for input 1
[Parsed_amerge_6 @ 0x7fa789c1a560] Input channel layouts overlap: output layout will be determined by the number of distinct input channels
[libx264 @ 0x7fa78a800600] using cpu capabilities: none!
[libx264 @ 0x7fa78a800600] profile High, level 4.2
[libx264 @ 0x7fa78a800600] 264 - core 129 - H.264/MPEG-4 AVC codec - Copyleft 2003-2013 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'out.mp4':
  Metadata:
    creationdate    : Mon Jun 10 14:44:12
    encoder         : Lavf55.8.102
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 480x180, q=-1--1, 16k tbn, 1k tbc
    Stream #0:1: Audio: aac (libfaac) ([64][0][0][0] / 0x0040), 44100 Hz, stereo, s16, 128 kb/s
Stream mapping:
  Stream #0:0 (flv) -> pad
  Stream #0:1 (nellymoser) -> amerge:in0
  Stream #1:0 (flv) -> pad
  Stream #1:1 (nellymoser) -> amerge:in1
  overlay -> Stream #0:0 (libx264)
  amerge -> Stream #0:1 (libfaac)
Press [q] to stop, [?] for help
[swscaler @ 0x7fa78a80f600] Warning: data is not aligned! This can lead to a speedloss
av_interleaved_write_frame(): Invalid argument