I noticed that this has something to do with the "raise on click" 
setting in Compiz.  If it's enabled, I can get this error.  If it's not 
enabled, no error.

And here's a better stack trace:

  # bind (standard-output stack-trace-on-signal debug-on-signal stack-
trace-on-error debug-on-error)
  # (unwind-protect ...)
  signal(error ("Selection aborted"))
  # bind (args datum)
  cerror("Selection aborted")
  apply(cerror "Selection aborted" nil)
  # bind (args datum)
  error("Selection aborted")
  (cond ((motion-event-p event) (if (and (not mouse-moved) (or (> (abs 
(- (event-x-pixel event) orig-x)) xthresh) (> (abs (- (event-y-pixel 
event) orig-y)) ythresh))) (setq mouse-moved t)) (if mouse-moved (mouse-
track-run-hook (quote mouse-track-drag-hook) overriding-hooks event 
mouse-track-click-count nil)) (mouse-track-set-timeout event)) ((and 
(timeout-event-p event) (eq (event-function event) (quote mouse-track-
scroll-undefined))) (if mouse-moved (mouse-track-run-hook (quote mouse-
track-drag-hook) overriding-hooks (event-object event) mouse-track-
click-count t)) (mouse-track-set-timeout (event-object event))) 
((button-release-event-p event) (setq mouse-track-up-time (event-
timestamp event)) (setq mouse-track-up-x (event-x-pixel event)) (setq 
mouse-track-up-y (event-y-pixel event)) (setq mouse-down nil) (mouse-
track-run-hook (quote mouse-track-up-hook) overriding-hooks event mouse-
track-click-count) (if mouse-moved (mouse-track-run-hook (quote mouse-
track-drag-up-hook) overriding-hooks event mouse-track-click-count) 
(mouse-track-run-hook (quote mouse-track-click-hook) overriding-hooks 
event mouse-track-click-count))) ((or (key-press-event-p event) (and 
(misc-user-event-p event) (eq (event-function event) (quote cancel-mode-
internal)))) (setq mdk-event event) (setq mdk-orig-event orig-event) 
(error "Selection aborted")) (t (dispatch-event event)))
  (while mouse-down (setq event (next-event event)) (cond ((motion-
event-p event) (if (and (not mouse-moved) (or (> (abs (- (event-x-pixel 
event) orig-x)) xthresh) (> (abs (- (event-y-pixel event) orig-y)) 
ythresh))) (setq mouse-moved t)) (if mouse-moved (mouse-track-run-hook 
(quote mouse-track-drag-hook) overriding-hooks event mouse-track-click-
count nil)) (mouse-track-set-timeout event)) ((and (timeout-event-p 
event) (eq (event-function event) (quote mouse-track-scroll-undefined))) 
(if mouse-moved (mouse-track-run-hook (quote mouse-track-drag-hook) 
overriding-hooks (event-object event) mouse-track-click-count t)) 
(mouse-track-set-timeout (event-object event))) ((button-release-event-p 
event) (setq mouse-track-up-time (event-timestamp event)) (setq mouse-
track-up-x (event-x-pixel event)) (setq mouse-track-up-y (event-y-pixel 
event)) (setq mouse-down nil) (mouse-track-run-hook (quote mouse-track-
up-hook) overriding-hooks event mouse-track-click-count) (if mouse-moved 
(mouse-track-run-hook (quote mouse-track-drag-up-hook) overriding-hooks 
event mouse-track-click-count) (mouse-track-run-hook (quote mouse-track-
click-hook) overriding-hooks event mouse-track-click-count))) ((or (key-
press-event-p event) (and (misc-user-event-p event) (eq (event-function 
event) (quote cancel-mode-internal)))) (setq mdk-event event) (setq mdk-
orig-event orig-event) (error "Selection aborted")) (t (dispatch-event 
event))))
  # (unwind-protect ...)
  (unwind-protect (while mouse-down (setq event (next-event event)) 
(cond ((motion-event-p event) (if (and (not mouse-moved) (or (> (abs (- 
(event-x-pixel event) orig-x)) xthresh) (> (abs (- (event-y-pixel event) 
orig-y)) ythresh))) (setq mouse-moved t)) (if mouse-moved (mouse-track-
run-hook (quote mouse-track-drag-hook) overriding-hooks event mouse-
track-click-count nil)) (mouse-track-set-timeout event)) ((and (timeout-
event-p event) (eq (event-function event) (quote mouse-track-scroll-
undefined))) (if mouse-moved (mouse-track-run-hook (quote mouse-track-
drag-hook) overriding-hooks (event-object event) mouse-track-click-count 
t)) (mouse-track-set-timeout (event-object event))) ((button-release-
event-p event) (setq mouse-track-up-time (event-timestamp event)) (setq 
mouse-track-up-x (event-x-pixel event)) (setq mouse-track-up-y (event-y-
pixel event)) (setq mouse-down nil) (mouse-track-run-hook (quote mouse-
track-up-hook) overriding-hooks event mouse-track-click-count) (if 
mouse-moved (mouse-track-run-hook (quote mouse-track-drag-up-hook) 
overriding-hooks event mouse-track-click-count) (mouse-track-run-hook 
(quote mouse-track-click-hook) overriding-hooks event mouse-track-click-
count))) ((or (key-press-event-p event) (and (misc-user-event-p event) 
(eq (event-function event) (quote cancel-mode-internal)))) (setq mdk-
event event) (setq mdk-orig-event orig-event) (error "Selection 
aborted")) (t (dispatch-event event)))) (if mouse-track-timeout-id 
(disable-timeout mouse-track-timeout-id)) (setq mouse-track-timeout-id 
nil) (and (buffer-live-p buffer) (save-excursion (set-buffer buffer) 
(let ((override (plist-get overriding-hooks (quote mouse-track-cleanup-
hook) Mouse-track-gensym))) (if (not (eq override Mouse-track-gensym)) 
(if (and (listp override) (not (eq (car override) (quote lambda)))) 
(mapc (function funcall) override) (funcall override)) (run-hooks (quote 
mouse-track-cleanup-hook)))))))
  # bind (mouse-moved orig-event mouse-grabbed-buffer buffer orig-y 
orig-x ythresh xthresh mouse-down)
  (let ((mouse-down t) (xthresh (eval mouse-track-x-threshold)) (ythresh 
(eval mouse-track-y-threshold)) (orig-x (event-x-pixel event)) (orig-y 
(event-y-pixel event)) (buffer (event-buffer event)) (mouse-grabbed-
buffer (event-buffer event)) (orig-event event) mouse-moved) (if (or 
(not mouse-track-up-x) (not mouse-track-up-y) (not mouse-track-up-time) 
(> (- (event-timestamp event) mouse-track-up-time) mouse-track-multi-
click-time) (> (abs (- mouse-track-up-x orig-x)) xthresh) (> (abs (- 
mouse-track-up-y orig-y)) ythresh)) (setq mouse-track-click-count 1) 
(setq mouse-track-click-count (1+ mouse-track-click-count))) (if (not 
(event-window event)) (error "Not over a window.")) (mouse-track-run-
hook (quote mouse-track-down-hook) overriding-hooks event mouse-track-
click-count) (unwind-protect (while mouse-down (setq event (next-event 
event)) (cond ((motion-event-p event) (if (and (not mouse-moved) (or (> 
(abs (- (event-x-pixel event) orig-x)) xthresh) (> (abs (- (event-y-
pixel event) orig-y)) ythresh))) (setq mouse-moved t)) (if mouse-moved 
(mouse-track-run-hook (quote mouse-track-drag-hook) overriding-hooks 
event mouse-track-click-count nil)) (mouse-track-set-timeout event)) 
((and (timeout-event-p event) (eq (event-function event) (quote mouse-
track-scroll-undefined))) (if mouse-moved (mouse-track-run-hook (quote 
mouse-track-drag-hook) overriding-hooks (event-object event) mouse-
track-click-count t)) (mouse-track-set-timeout (event-object event))) 
((button-release-event-p event) (setq mouse-track-up-time (event-
timestamp event)) (setq mouse-track-up-x (event-x-pixel event)) (setq 
mouse-track-up-y (event-y-pixel event)) (setq mouse-down nil) (mouse-
track-run-hook (quote mouse-track-up-hook) overriding-hooks event mouse-
track-click-count) (if mouse-moved (mouse-track-run-hook (quote mouse-
track-drag-up-hook) overriding-hooks event mouse-track-click-count) 
(mouse-track-run-hook (quote mouse-track-click-hook) overriding-hooks 
event mouse-track-click-count))) ((or (key-press-event-p event) (and 
(misc-user-event-p event) (eq (event-function event) (quote cancel-mode-
internal)))) (setq mdk-event event) (setq mdk-orig-event orig-event) 
(error "Selection aborted")) (t (dispatch-event event)))) (if mouse-
track-timeout-id (disable-timeout mouse-track-timeout-id)) (setq mouse-
track-timeout-id nil) (and (buffer-live-p buffer) (save-excursion (set-
buffer buffer) (let ((override (plist-get overriding-hooks (quote mouse-
track-cleanup-hook) Mouse-track-gensym))) (if (not (eq override Mouse-
track-gensym)) (if (and (listp override) (not (eq (car override) (quote 
lambda)))) (mapc (function funcall) override) (funcall override)) (run-
hooks (quote mouse-track-cleanup-hook))))))))
  # bind (overriding-hooks event)
  mouse-track(#<keypress-event F 0x9b7b>)
  # bind (command-debug-status)
  call-interactively(mouse-track)
  (dispatch-event "[internal]")
  # (condition-case ... . error)
  # (catch top-level ...)

Ignore the references to mdk-event and mdk-orig-event.  I added those to 
mouse-track so that I could see if there was a pattern to the events 
that trigger the error.  The only thing I've noticed is that they're 
always keypress events.