I am having this same problem with another Java application. This makes natty unusable. Two of my other coworkers are having a similar problem.

----- from xsession-errors -----
(unity-window-decorator:9754): GLib-GObject-CRITICAL **: g_object_get_data: assertion `G_IS_OBJECT (object)' failed
(unity-window-decorator:9754): GLib-GObject-WARNING **: invalid uninstantiatable type `<invalid>' in cast to `GObject'
(unity-window-decorator:9754): GLib-GObject-CRITICAL **: g_object_get_data: assertion `G_IS_OBJECT (object)' failed
Segmentation fault

---- the last 20 or so system calls from ltrace (all on the same level) ----

        XRenderFreePicture(0x655ef0, 0x4400c4b, 0x7e27f0, 938432, 0x7ee430)                         = 0
        g_free(0x7d4fe0, 0x4400c4b, 153, 938432, 0x7ee430)                                          = 0x7d0240
        g_type_check_instance_cast(0x7be8b0, 80, 0, 0, 0x7d4fd0)                                    = 0x7be8b0
        g_object_unref(0x7be8b0, 0x697030, 1, 0x692eb0, 0x7d4fd0)                                   = 1
        cairo_pattern_destroy(0x7d3880, 16, 15, 10, 176)                                            = 0
        g_type_check_instance_cast(0x7dd6d0, 80, 1, 0x7fa22f5236a0, 56)                             = 0x7dd6d0
        g_object_unref(0x7dd6d0, 0x6e5860, 2, 0x6ddf20, 56)                                         = 1
        g_type_check_instance_cast(0x7d9590, 80, 43, 2, 48)                                         = 0x7d9590
        g_object_unref(0x7d9590, 0x794a50, 1, 0x690f40, 48)                                         = 1
        g_slist_remove(0, 0x7dd100, 2, 1, 48)                                                       = 0
        g_type_check_instance_cast(0x7d5070, 80, 2, 1, 48)                                          = 0x7d5070
        g_object_set_data(0x7d5070, 0x418304, 0, 0x6af8e0, 48)                                      = 0
        gdk_error_trap_push(0x7fa22ea009e8, 0, 0x7fa22ea009e8, 1, 32)                               = 0x7fa230d1a310
        wnck_window_get_xid(0x7d5070, 0, 0x7fa230d1a5e4, 1, 32)                                     = 0x5600101
        XDeleteProperty(0x655ef0, 0x5600101, 445, 1, 32)                                            = 1
        gdk_display_get_default(0x655ef0, 0x5600101, 0x65cc4c, 1, 32)                               = 0x663000
        gdk_display_sync(0x663000, 0x5600101, 0x65cc4c, 1, 32)                                      = 1
        gdk_error_trap_pop(0x7fa22e4e51c0, 0, 1, 1, 0x7e63a0)                                       = 3
        g_free(0x7dd100, 0, 0x7fa230d1a310, 1, 0x7e63a0)                                            = 833
        gdk_display_get_default(0x6b1020, 0x7d5180, 0, 0x7dd950, 0x7ffffd487580)                    = 0x663000
        gdk_x11_display_get_xdisplay(0x663000, 0x7d5180, 0, 0x7dd950, 0x7ffffd487580)               = 0x655ef0
        g_type_check_instance_cast(0x7d5180, 80, 0x63d650, 1, 0x7ffffd487580)                       = 0x7d5180
        g_object_get_data(0x7d5180, 0x418304, 1, 0x6af8e0, 0x7ffffd487580)                          = 0x7e6010
        g_type_check_instance_cast(0x7d5290, 80, 0x7fa22ea009e8, 0, 0x7fa22ea009e8
(unity-window-decorator:25228): GLib-GObject-WARNING **: invalid unclassed pointer in cast to `GObject'
)                 = 0x7d5290
        g_object_get_data(0x7d5290, 0x418304, 0x7fa22dee42c0, 0, 0x7bcfb0
(unity-window-decorator:25228): GLib-GObject-CRITICAL **: g_object_get_data: assertion `G_IS_OBJECT (object)' failed
)                          = 0
--- SIGSEGV (Segmentation fault) ---


---- a gdb backtrace from the same process as the above ltrace ----

#0  0x0000000000415d6f in ?? ()
#1  0x00007fa22f02181c in g_closure_invoke (closure=0x6b0560, return_value=0x0, n_param_values=2, param_values=0x7dd950, invocation_hint=0x7ffffd487580)
    at /build/buildd/glib2.0-2.28.6/./gobject/gclosure.c:767
#2  0x00007fa22f033019 in signal_emit_unlocked_R (node=<value optimized out>, detail=0, instance=0x6b1020, emission_return=0x0, instance_and_params=0x7dd950)
    at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:3252
#3  0x00007fa22f03c258 in g_signal_emit_valist (instance=<value optimized out>, signal_id=<value optimized out>, detail=<value optimized out>, 
    var_args=<value optimized out>) at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:2983
#4  0x00007fa22f03c41f in g_signal_emit (instance=<value optimized out>, signal_id=<value optimized out>, detail=<value optimized out>)
    at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:3040
#5  0x00007fa231374d44 in ?? () from /usr/lib/libwnck-1.so.22
#6  0x00007fa2313753d4 in ?? () from /usr/lib/libwnck-1.so.22
#7  0x00007fa22e755bcd in g_main_dispatch (context=0x66f770) at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:2440
#8  g_main_context_dispatch (context=0x66f770) at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:3013
#9  0x00007fa22e7563a8 in g_main_context_iterate (context=0x66f770, block=<value optimized out>, dispatch=1, self=<value optimized out>)
    at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:3091
#10 0x00007fa22e7569f2 in g_main_loop_run (loop=0x73dfa0) at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:3299
#11 0x00007fa230e50af7 in IA__gtk_main () at /build/buildd/gtk+2.0-2.24.4/gtk/gtkmain.c:1257
#12 0x0000000000409864 in main ()