The path used by Aquamacs Emacs to load the plugin is as follows:
/Library/Application Support/Emacs/ec-emacs/site-lisp/xxx.el
(with 'Emacs' being capitalized)

However, the plugin installs in
/Library/Application Support/emacs/...
(where emacs is NOT capitalized)

Thus, the bug will remain dormant on a default HFS+ filesystem, but  
it will
case a failure to load the plugin on a case-sensitive filesystem  
(whether
a case-sensitive HFS+ or Unix filesystem).



In GNU Emacs 22.1.50.1 (powerpc-apple-darwin7.9.0, Carbon Version 1.6.0)
  of 2007-10-02 on applecore.inf.ed.ac.uk - Aquamacs Distribution 1.2a
Windowing system distributor `Apple Inc.', version 10.4.11
configured using `configure  '--without-x' '--prefix=/usr/local''

Important settings:
   value of $LC_ALL: nil
   value of $LC_COLLATE: nil
   value of $LC_CTYPE: nil
   value of $LC_MESSAGES: nil
   value of $LC_MONETARY: nil
   value of $LC_NUMERIC: nil
   value of $LC_TIME: nil
   value of $LANG: nil
   locale-coding-system: iso-8859-1
   default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
   msb-mode: t
   one-buffer-one-frame-mode: t
   smart-frame-positioning-mode: t
   aquamacs-styles-mode: t
   recentf-mode: t
   encoded-kbd-mode: t
   osx-key-mode: t
   show-paren-mode: t
   delete-selection-mode: t
   pc-selection-mode: t
   tooltip-mode: t
   mac-input-method-mode: t
   tool-bar-mode: t
   mouse-wheel-mode: t
   menu-bar-mode: t
   file-name-shadow-mode: t
   global-font-lock-mode: t
   font-lock-mode: t
   blink-cursor-mode: t
   unify-8859-on-encoding-mode: t
   utf-translate-cjk-mode: t
   auto-compression-mode: t
   column-number-mode: t
   line-number-mode: t

Recent input:
<help-echo> <help-echo> A-x C-x b <return> <wheel-down>
<double-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <wheel-up> <double-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <wheel-up> <double-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<wheel-up> <double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<wheel-up> <double-wheel-up> <triple-wheel-up> <wheel-up>
<double-wheel-up> <triple-wheel-up> <switch-frame>
<help-echo> <switch-frame> <down-mouse-1> <mouse-movement>
<mouse-movement> <drag-mouse-1> <down-mouse-1> <mouse-1>
<down-mouse-1> <mouse-movement> <mouse-movement> <drag-mouse-1>
A-c <help-echo> <help-echo> <wheel-down> <double-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <wheel-down>
<double-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<wheel-up> <double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<wheel-down> <double-wheel-down> <triple-wheel-down>
<triple-wheel-down> <wheel-down> <double-wheel-down>
<triple-wheel-down> <triple-wheel-down> <wheel-down>
<double-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <wheel-down> <double-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <wheel-down> <double-wheel-down>
<triple-wheel-down> <triple-wheel-down> <wheel-up>
<double-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <wheel-down> <double-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <triple-wheel-down> <wheel-down>
<double-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <wheel-down> <double-wheel-down>
<triple-wheel-down> <triple-wheel-down> <triple-wheel-down>
<triple-wheel-down> <wheel-up> <double-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
<triple-wheel-up> <triple-wheel-up> <triple-wheel-up>
C-s c u a C-s C-s <help-echo> <help-echo> <help-echo>
<switch-frame> <wheel-up> <double-wheel-up> <triple-wheel-up>
<wheel-up> <double-wheel-up> <switch-frame> <switch-frame>
<down-mouse-1> <mouse-movement> <mouse-1> <help-echo>
<menu-bar> <help-menu> <send-emacs-bug-report>

Recent messages:
Loading /Users/defago/Library/Preferences/Aquamacs Emacs/ 
customizations.el (source)...done
Loading /Users/defago/Library/Preferences/Aquamacs Emacs/frame- 
positions.el (source)...done
Aquamacs is based on GNU Emacs 22, a part of the GNU/Linux system.
It is Free Software: you can improve and redistribute it under the  
GNU General
Public License, version 3 or later. Copyright (C) 2007 Free Software  
Foundation,
Inc. (C) 2007 D. Reitter. No Warranty.
The mark is not set now, so there is no region
Mark saved where search started
byte-code: Beginning of buffer [2 times]
Loading emacsbug...done