I clicked on both the volumes and opened two nautilus windows, then unmounted one of the two, the other remained there on the desktop, then I closed the first window, then the second and I got this crash report - if it can be of help:

Distribution: Ubuntu 6.10 (edgy)
Gnome Release: 2.16.1 2006-10-02 (Ubuntu)
BugBuddy Version: 2.16.0

Memory status: size: 129650688 vsize: 0 resident: 129650688 share: 0 rss: 37924864 rss_rlim: 0
CPU usage: start_time: 1168511884 rtime: 0 utime: 810 stime: 0 cutime:764 cstime: 0 timeout: 46 it_real_value: 0 frequency: 0

Backtrace was generated from '/usr/bin/nautilus'

Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1226701136 (LWP 4737)]
0xffffe410 in __kernel_vsyscall ()
#0  0xffffe410 in __kernel_vsyscall ()
#1  0xb76b634b in __waitpid_nocancel ()
   from /lib/tls/i686/cmov/libpthread.so.0
#2  0xb7e4d1b6 in gnome_gtk_module_info_get () from /usr/lib/libgnomeui-2.so.0
#3  <signal handler called>
#4  0xb76cc9a1 in IA__g_object_unref (_object=0x8ada328) at gobject.c:1737
#5  0xb76400f1 in IA__g_list_foreach (list=0x897a280, 
    func=0x8064d20 <g_object_unref@plt>, user_data=0x0) at glist.c:495
#6  0xb7c953cc in gtk_ui_manager_finalize (object=0x8831190)
    at gtkuimanager.c:392
#7  0xb76ccaec in IA__g_object_unref (_object=0x8831190) at gobject.c:1788
#8  0x0809d28d in nautilus_window_finalize (object=0x86e6c88)
    at nautilus-window.c:635
#9  0xb76ccaec in IA__g_object_unref (_object=0x86e6c88) at gobject.c:1788
#10 0xb7b82f99 in IA__gtk_main_do_event (event=0x8cbfad8) at gtkmain.c:1395
#11 0xb7a0c7ea in gdk_event_dispatch (source=0x81961b8, callback=0, 
    user_data=0x0) at gdkevents-x11.c:2320
#12 0xb7642802 in IA__g_main_context_dispatch (context=0x8196200)
    at gmain.c:2045
#13 0xb76457df in g_main_context_iterate (context=0x8196200, block=1, 
    dispatch=1, self=0x8177298) at gmain.c:2677
#14 0xb7645b89 in IA__g_main_loop_run (loop=0x81e7bb0) at gmain.c:2881
#15 0xb7b83574 in IA__gtk_main () at gtkmain.c:1024
#16 0x0807bb4a in main (argc=9, argv=0xbfbdd6c4) at nautilus-main.c:372
#17 0xb73ca8cc in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
#18 0x08067621 in _start ()

Thread 1 (Thread -1226701136 (LWP 4737)):
#0  0xffffe410 in __kernel_vsyscall ()
No symbol table info available.
#1  0xb76b634b in __waitpid_nocancel ()
   from /lib/tls/i686/cmov/libpthread.so.0
No symbol table info available.
#2  0xb7e4d1b6 in gnome_gtk_module_info_get () from /usr/lib/libgnomeui-2.so.0
No symbol table info available.
#3  <signal handler called>
No symbol table info available.
#4  0xb76cc9a1 in IA__g_object_unref (_object=0x8ada328) at gobject.c:1737
	__r = <value optimized out>
	object = (GObject *) 0x8ada328
	__PRETTY_FUNCTION__ = "IA__g_object_unref"
#5  0xb76400f1 in IA__g_list_foreach (list=0x897a280, 
    func=0x8064d20 <g_object_unref@plt>, user_data=0x0) at glist.c:495
	next = (GList *) 0x0
#6  0xb7c953cc in gtk_ui_manager_finalize (object=0x8831190)
    at gtkuimanager.c:392
No locals.
#7  0xb76ccaec in IA__g_object_unref (_object=0x8831190) at gobject.c:1788
	object = (GObject *) 0x8831190
	__PRETTY_FUNCTION__ = "IA__g_object_unref"
#8  0x0809d28d in nautilus_window_finalize (object=0x86e6c88)
    at nautilus-window.c:635
	window = (NautilusWindow *) 0x86e6c88
#9  0xb76ccaec in IA__g_object_unref (_object=0x86e6c88) at gobject.c:1788
	object = (GObject *) 0x86e6c88
	__PRETTY_FUNCTION__ = "IA__g_object_unref"
#10 0xb7b82f99 in IA__gtk_main_do_event (event=0x8cbfad8) at gtkmain.c:1395
	event_widget = (GtkWidget *) 0x86e6c88
	grab_widget = (GtkWidget *) 0x86e6c88
	window_group = (GtkWindowGroup *) 0x83007d0
	next_event = <value optimized out>
	rewritten_event = (GdkEvent *) 0x0
	tmp_list = <value optimized out>
	__PRETTY_FUNCTION__ = "IA__gtk_main_do_event"
#11 0xb7a0c7ea in gdk_event_dispatch (source=0x81961b8, callback=0, 
    user_data=0x0) at gdkevents-x11.c:2320
	display = <value optimized out>
	event = (GdkEvent *) 0x8cbfad8
#12 0xb7642802 in IA__g_main_context_dispatch (context=0x8196200)
    at gmain.c:2045
No locals.
#13 0xb76457df in g_main_context_iterate (context=0x8196200, block=1, 
    dispatch=1, self=0x8177298) at gmain.c:2677
	got_ownership = <value optimized out>
	max_priority = 0
	timeout = 0
	some_ready = 1
	nfds = <value optimized out>
	allocated_nfds = <value optimized out>
	fds = (GPollFD *) 0x82b7948
	__PRETTY_FUNCTION__ = "g_main_context_iterate"
#14 0xb7645b89 in IA__g_main_loop_run (loop=0x81e7bb0) at gmain.c:2881
	got_ownership = -1217719328
	self = (GThread *) 0x8177298
	__PRETTY_FUNCTION__ = "IA__g_main_loop_run"
#15 0xb7b83574 in IA__gtk_main () at gtkmain.c:1024
	tmp_list = (GList *) 0x81889e8
	functions = (GList *) 0x0
	init = (GtkInitFunction *) 0x0
	loop = (GMainLoop *) 0x81e7bb0
#16 0x0807bb4a in main (argc=9, argv=0xbfbdd6c4) at nautilus-main.c:372
	kill_shell = 0
	restart_shell = 0
	no_default_window = 1
	browser_window = 0
	no_desktop = 0
	startup_id = <value optimized out>
	startup_id_copy = 0x81889e8 "\032"
	session_to_load = 0x8185f48 "/home/vincenzo/.nautilus/savedYHtWSJ"
	geometry = (gchar *) 0x0
	remaining = (const gchar **) 0x0
	perform_self_check = 0
	context = <value optimized out>
	application = (NautilusApplication *) 0x81b07b0
	program = (GnomeProgram *) 0x8177428
	options = {{long_name = 0x813f483 "check", short_name = 99 'c', 
    flags = 0, arg = G_OPTION_ARG_NONE, arg_data = 0xbfbdd590, 
    description = 0x813f4ac "Perform a quick set of self-check tests.", 
    arg_description = 0x0}, {long_name = 0x8142424 "geometry", 
    short_name = 103 'g', flags = 0, arg = G_OPTION_ARG_STRING, 
    arg_data = 0xbfbdd598, 
    description = 0x813f4d8 "Create the initial window with the given geometry.", arg_description = 0x813f305 "GEOMETRY"}, {
    long_name = 0x813f30e "no-default-window", short_name = 110 'n', 
    flags = 0, arg = G_OPTION_ARG_NONE, arg_data = 0xbfbdd5a8, 
    description = 0x813f50c "Only create windows for explicitly specified URIs.", arg_description = 0x0}, {long_name = 0x813f320 "no-desktop", 
    short_name = 0 '\0', flags = 0, arg = G_OPTION_ARG_NONE, 
    arg_data = 0xbfbdd5a0, 
    description = 0x813f540 "Do not manage the desktop (ignore the preference set in the preferences dialog).", arg_description = 0x0}, {
    long_name = 0x814147e "browser", short_name = 0 '\0', flags = 0, 
    arg = G_OPTION_ARG_NONE, arg_data = 0xbfbdd5a4, 
    description = 0x813f32b "open a browser window.", arg_description = 0x0}, 
  {long_name = 0x813f48b "quit", short_name = 113 'q', flags = 0, 
    arg = G_OPTION_ARG_NONE, arg_data = 0xbfbdd5b0, 
    description = 0x813f342 "Quit Nautilus.", arg_description = 0x0}, {
    long_name = 0x813f492 "restart", short_name = 0 '\0', flags = 1, 
    arg = G_OPTION_ARG_NONE, arg_data = 0xbfbdd5ac, 
    description = 0x813f351 "Restart Nautilus.", arg_description = 0x0}, {
    long_name = 0x8143715 "", short_name = 0 '\0', flags = 0, 
    arg = G_OPTION_ARG_STRING_ARRAY, arg_data = 0xbfbdd594, 
    description = 0x0, arg_description = 0x813f363 "[URI...]"}, {
    long_name = 0x813ba0a "load-session", short_name = 108 'l', flags = 0, 
    arg = G_OPTION_ARG_STRING, arg_data = 0xbfbdd59c, 
    description = 0x813f594 "Load a saved session from the specified file. Implies \"--no-default-window\".", arg_description = 0x813f36c "FILENAME"}, {
    long_name = 0x0, short_name = 0 '\0', flags = 0, arg = G_OPTION_ARG_NONE, 
    arg_data = 0x0, description = 0x0, arg_description = 0x0}}
#17 0xb73ca8cc in __libc_start_main () from /lib/tls/i686/cmov/libc.so.6
No symbol table info available.
#18 0x08067621 in _start ()
No symbol table info available.
#0  0xffffe410 in __kernel_vsyscall ()