I started awn from the command line with the command avant-window-navigator and here is the output.  I tried to open some files with stacks and also tried to remove them.

rie-rie@dell:~$ avant-window-navigator
Screen is composited.
LOADED : /usr/share/applications/ooo-writer.desktop
LOADED : /usr/share/applications/rhythmbox.desktop
LOADED : /usr/share/applications/ooo-calc.desktop
LOADED : /usr/share/applications/ooo-impress.desktop
LOADED : /usr/share/applications/firefox.desktop
LOADED : /usr/share/applications/ooo-draw.desktop
APPLET : /usr/local/lib/awn/applets/taskman.desktop
APPLET : /usr/local/lib/awn/applets/stacks.desktop
APPLET : /usr/local/lib/awn/applets/main-menu.desktop
APPLET : /usr/local/lib/awn/applets/places.desktop
Please inform the developer(s) of the applet 'Stacks Applet' that the .desktop file associated with their applet need to be updated per the Applet Development Guidelines on the AWN Wiki.
(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)
Setting dialog type to  2

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)
Traceback (most recent call last):
  File "/usr/local/lib/awn/applets/stacks/stacks_backend.py", line 127, in _deleted_cb
    if self.remove([vfs_uri]):
  File "/usr/local/lib/awn/applets/stacks/stacks_backend_file.py", line 73, in remove
    return Backend.remove(self, vfs_uris)
  File "/usr/local/lib/awn/applets/stacks/stacks_backend.py", line 236, in remove
    self.emit("item-removed", None) # iter not valid any more?
TypeError: could not convert type NoneType to GtkTreeIter required for parameter 0
Traceback (most recent call last):
  File "/usr/local/lib/awn/applets/stacks/stacks_backend.py", line 127, in _deleted_cb
    if self.remove([vfs_uri]):
  File "/usr/local/lib/awn/applets/stacks/stacks_backend_file.py", line 73, in remove
    return Backend.remove(self, vfs_uris)
  File "/usr/local/lib/awn/applets/stacks/stacks_backend.py", line 236, in remove
    self.emit("item-removed", None) # iter not valid any more?
TypeError: could not convert type NoneType to GtkTreeIter required for parameter 0
Traceback (most recent call last):
  File "/usr/local/lib/awn/applets/stacks/stacks_backend.py", line 127, in _deleted_cb
    if self.remove([vfs_uri]):
  File "/usr/local/lib/awn/applets/stacks/stacks_backend_file.py", line 73, in remove
    return Backend.remove(self, vfs_uris)
  File "/usr/local/lib/awn/applets/stacks/stacks_backend.py", line 236, in remove
    self.emit("item-removed", None) # iter not valid any more?
TypeError: could not convert type NoneType to GtkTreeIter required for parameter 0

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)
AwnWindow: drag_data_received_handl
 Receiving string: file:///home/rie-rie/Images/You%20Rock%20My%20Globe.png
Desktop file: /home/rie-rie/Images/You Rock My Globe.p
Error : Error reading file 'file:///home/rie-rie/Images/You%20Rock%20My%20Globe.p': File not found
(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)

(avant-window-navigator:9589): Wnck-WARNING **: Unhandled action type (nil)
Traceback (most recent call last):
  File "/usr/local/lib/awn/applets/stacks/stacks_gui_curved.py", line 581, in item_clear_cb
    self.applet.backend.remove([uri])
  File "/usr/local/lib/awn/applets/stacks/stacks_backend_file.py", line 73, in remove
    return Backend.remove(self, vfs_uris)
  File "/usr/local/lib/awn/applets/stacks/stacks_backend.py", line 236, in remove
    self.emit("item-removed", None) # iter not valid any more?
TypeError: could not convert type NoneType to GtkTreeIter required for parameter 0