backtrace:

Breakpoint 3, 0xb6fc3f66 in _XError () from /usr/lib/i386-linux-gnu/libX11.so.6
(gdb) bt
#0  0xb6fc3f66 in _XError () from /usr/lib/i386-linux-gnu/libX11.so.6
#1  0xb6fc10ea in ?? () from /usr/lib/i386-linux-gnu/libX11.so.6
#2  0xb6fc1ca5 in _XReply () from /usr/lib/i386-linux-gnu/libX11.so.6
#3  0xb651bc8b in XGrabDevice () from /usr/lib/i386-linux-gnu/libXi.so.6
#4  0xb73aa931 in ?? () from /usr/lib/libgdk-x11-2.0.so.0
#5  0xb7397c63 in ?? () from /usr/lib/libgdk-x11-2.0.so.0
#6  0xb7378d41 in gdk_pointer_grab () from /usr/lib/libgdk-x11-2.0.so.0
#7  0x081de10a in sp_canvas_item_grab (item=0x9d1a120, event_mask=3844, 
    cursor=0x0, etime=1266439) at display/sp-canvas.cpp:556
#8  0x0858705c in sp_select_context_root_handler (event_context=0x9d17a20, 
    event=0xa599940) at select-context.cpp:509
#9  0x0808dea7 in sp_event_context_virtual_root_handler (
    event_context=0x9d17a20, event=0xa599940) at event-context.cpp:965
#10 0x08518357 in sp_desktop_root_handler (event=0xa599940, desktop=0x8fe9db0)
    at desktop-events.cpp:71
#11 0x08248418 in sp_marshal_BOOLEAN__POINTER (closure=0x9d78778, 
    return_value=0xbfffef1c, n_param_values=2, param_values=0xa5a80c8, 
    invocation_hint=0xbfffedd0, marshal_data=0x0) at helper/sp-marshal.cpp:124
#12 0xb6d76372 in g_closure_invoke ()
   from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#13 0xb6d89048 in ?? () from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
---Type <return> to continue, or q <return> to quit---
#14 0xb6d918d7 in g_signal_emit_valist ()
   from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#15 0xb6d91cc2 in g_signal_emit ()
   from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#16 0x081dcf85 in emit_event (canvas=0xbfffefb4, event=0xa5980f8)
    at display/sp-canvas.cpp:1376
#17 0xb7595a04 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#18 0xb6d74cc7 in ?? () from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#19 0xb6d76372 in g_closure_invoke ()
   from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#20 0xb6d88e45 in ?? () from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#21 0xb6d918d7 in g_signal_emit_valist ()
   from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#22 0xb6d91cc2 in g_signal_emit ()
   from /usr/lib/i386-linux-gnu/libgobject-2.0.so.0
#23 0xb76ca836 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#24 0xb7593b8d in gtk_propagate_event () from /usr/lib/libgtk-x11-2.0.so.0
#25 0xb75941af in gtk_main_do_event () from /usr/lib/libgtk-x11-2.0.so.0
#26 0xb738fa0a in ?? () from /usr/lib/libgdk-x11-2.0.so.0
#27 0xb6cc4aa8 in g_main_context_dispatch ()
   from /lib/i386-linux-gnu/libglib-2.0.so.0
---Type <return> to continue, or q <return> to quit---
#28 0xb6cc5270 in ?? () from /lib/i386-linux-gnu/libglib-2.0.so.0
#29 0xb6cc592b in g_main_loop_run () from /lib/i386-linux-gnu/libglib-2.0.so.0
#30 0xb7592c39 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#31 0xb7bae357 in Gtk::Main::run_impl() () from /usr/lib/libgtkmm-2.4.so.1
#32 0xb7baed42 in Gtk::Main::run() () from /usr/lib/libgtkmm-2.4.so.1
#33 0x08083183 in sp_main_gui (argc=1, argv=0xbffff7a4) at main.cpp:978
#34 0x08084900 in main (argc=2, argv=0xbffff7a4) at main.cpp:709

(gdb) frame 7
#7  0x081de10a in sp_canvas_item_grab (item=0x9d1a120, event_mask=3844, 
    cursor=0x0, etime=1266439) at display/sp-canvas.cpp:556
556	                      NULL, cursor, etime);

(gdb) info frame
Stack level 7, frame at 0xbfffea10:
 eip = 0x81de10a in sp_canvas_item_grab (display/sp-canvas.cpp:556); 
    saved eip 0x858705c
 called by frame at 0xbfffebd0, caller of frame at 0xbfffe9d0
 source language c++.
 Arglist at 0xbfffea08, args: item=0x9d1a120, event_mask=3844, cursor=0x0, 
    etime=1266439
 Locals at 0xbfffea08, Previous frame's sp is 0xbfffea10
 Saved registers:
  ebx at 0xbfffe9fc, ebp at 0xbfffea08, esi at 0xbfffea00, edi at 0xbfffea04,
  eip at 0xbfffea0c