Heap corruption crash on Windows

[Phil Wise]

When transcoding a h264 video on Windows, ffmpeg2theora crashed with what appears to be a heap corruption bug:

ChildEBP RetAddr
0028ea54 774b35a7 ntdll!RtlpCoalesceFreeBlocks+0x35
0028eb4c 774b3492 ntdll!RtlpFreeHeap+0x1f4
0028eb6c 760f98cd ntdll!RtlFreeHeap+0x142
0028ebb8 0040a849 msvcrt!free+0xcd
WARNING: Stack unwind information not available. Following frames may be wrong.
0028ebd8 0040d146 ffmpeg2theora+0xa849
0028fec8 004013ea ffmpeg2theora+0xd146
0028ff88 76a9339a ffmpeg2theora+0x13ea
0028ff94 774b9ef2 kernel32!BaseThreadInitThunk+0xe
0028ffd4 774b9ec5 ntdll!__RtlUserThreadStart+0x70
0028ffec 00000000 ntdll!_RtlUserThreadStart+0x1b

Do you have symbol files for the builds of ffmpeg2theora.

The video appears to have encoded correctly, so I suspect that this happened right at the end of the process.
I'm running ffmpeg2theora v0.29

ffmpeg2theora 0.29

        Xiph.Org libtheora 1.2.0alpha 20100924 (Ptalarbvorm)
        Xiph.Org libVorbis 1.3.3
        FFmpeg libavcodec 54.31.100
        FFmpeg libavformat 54.14.100

The video is too big to post here, but I'm happy to try again on a debug or newer build if that would help.

I've attached the minidump for WinDBG