I think I am running into this bug.  Backtrace attached.

In GNU Emacs 24.3.93.1 (x86_64-unknown-cygwin)
  of 2014-09-25 on AGAULAND-NZCD
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
  `configure --enable-checking --with-w32 --without-gnutls 'CFLAGS=-O0
  -ggdb''

Important settings:
   value of $LANG: en_US.UTF-8
   locale-coding-system: utf-8-unix

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mail-utils network-stream starttls
tls erc-track erc-spelling flyspell ispell erc-services erc-ring
erc-networks erc-netsplit erc-menu erc-match erc-log erc-list
erc-pcomplete pcomplete erc-button erc-fill erc-stamp wid-edit erc-join
erc-autoaway erc-goodies erc erc-backend erc-compat format-spec
auth-source eieio byte-opt bytecomp byte-compile cconv eieio-core
gnus-util mm-util mail-prsvr password-cache thingatpt pp smex jka-compr
view vc-git paredit dired vc-dispatcher vc-svn hideshow easy-mmode
undo-tree diff python skeleton derived pcase rx json
browse-kill-ring-autoloads ido-ubiquitous-autoloads info 
magit-autoloads
git-rebase-mode-autoloads git-commit-mode-autoloads paredit-autoloads
smex-autoloads undo-tree-autoloads package server cc-styles cc-align
cc-engine cc-langs cc-vars cc-defs cc-bytecomp appt diary-lib
diary-loaddefs cal-menu easymenu calendar cal-loaddefs advice help-fns
ido header-file find-file gtags mu cl-macs edmacro kmacro cl gv comint
ansi-color ring saveplace paren savehist avoid time battery desktop
frameset cl-loaddefs cl-lib cus-start cus-load time-date tooltip
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
w32-common-fns disp-table w32-win w32-vars tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode prog-mode 
register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core frame cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process gfilenotify w32
multi-tty emacs)

Memory information:
((conses 16 306063 12290)
  (symbols 48 32658 0)
  (miscs 40 94 393)
  (strings 32 69458 8600)
  (string-bytes 1 1969107)
  (vectors 16 26932)
  (vector-slots 8 574485 16135)
  (floats 8 145 299)
  (intervals 56 1550 376)
  (buffers 960 24))