Hi folks,

I get a similar error by following this sequence in 24.4.1:
1. emacs -Q
2. M-x icomplete-mode
3. M-x set-variable icomplete-show-matches-on-no-input t
4. C-x C-f C-a C-k

Version and settings are below.

Regards,
Jeremy

In GNU Emacs 24.4.1 (i686-pc-mingw32)
 of 2014-10-24 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/usr'

Important settings:
  value of $LANG: ENG
  locale-coding-system: cp1252

Major mode: Lisp Interaction

Minor modes in effect:
  icomplete-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
M-x i c o m p l e t e SPC m o d e <return> M-x s e
t SPC v a r <return> i c o m p l e t e SPC s h o w
<return> t <return> C-x C-f C-a C-k C-g M-x r e p o
t <backspace> r t <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Icomplete mode enabled
Error in post-command-hook (icomplete-post-command-hook): (invalid-function
(#("./" 0 1 (face (completions-first-difference))) #("../" 0 1 (face
(completions-first-difference))) #("addpm.exe" 0 1 (face
(completions-first-difference))) #("ctags.exe" 0 1 (face
(completions-first-difference))) #("emacs.exe" 0 1 (face
(completions-first-difference))) #("etags.exe" 0 1 (face
(completions-first-difference))) #("libXpm.dll" 0 1 (face
(completions-first-difference))) #("ebrowse.exe" 0 1 (face
(completions-first-difference))) #("runemacs.exe" 0 1 (face
(completions-first-difference))) #("emacs-24.4.exe" 0 1 (face
(completions-first-difference))) #("grep-changelog" 0 1 (face
(completions-first-difference))) #("runvanilla.lnk" 0 1 (face
(completions-first-difference))) #("emacsclient.exe" 0 1 (face
(completions-first-difference))) #("emacsclientw.exe" 0 1 (face
(completions-first-difference)))))
Quit

Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
mail-prsvr mail-utils cus-edit easymenu wid-edit cl-loaddefs cl-lib
help-fns mule-util cus-start cus-load icomplete time-date tooltip
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel dos-w32
ls-lisp 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
w32notify w32 multi-tty emacs)

Memory information:
((conses 8 94199 5225)
 (symbols 32 19208 0)
 (miscs 32 36 138)
 (strings 16 14989 3911)
 (string-bytes 1 391743)
 (vectors 8 10790)
 (vector-slots 4 394081 3824)
 (floats 8 65 84)
 (intervals 28 212 41)
 (buffers 508 11))