Steps to reproduce:
1. right-click on the plugin icon
2. select "About"
Segmentation fault.

A backtrace:
Program terminated with signal 11, Segmentation fault.
#0  0xb6fdaa0b in strlen () from /lib/libc.so.6
(gdb) bt
#0  0xb6fdaa0b in strlen () from /lib/libc.so.6
#1  0xb712d1db in g_strdup () from /usr/lib/libglib-2.0.so.0
#2  0xb712f444 in g_strdupv () from /usr/lib/libglib-2.0.so.0
#3  0xb74054ef in gtk_about_dialog_set_authors () from /usr/lib/libgtk-x11-2.0.so.0
#4  0x08050c3a in xfce_xkb_about ()
#5  0xb71c3c4c in g_cclosure_marshal_VOID__VOID () from /usr/lib/libgobject-2.0.so.0
#6  0xb71a7a72 in g_closure_invoke () from /usr/lib/libgobject-2.0.so.0
#7  0xb71ba8a0 in ?? () from /usr/lib/libgobject-2.0.so.0
#8  0xb71c3306 in g_signal_emit_valist () from /usr/lib/libgobject-2.0.so.0
#9  0xb71c34b2 in g_signal_emit () from /usr/lib/libgobject-2.0.so.0
#10 0xb781d384 in ?? () from /usr/lib/libxfce4panel-1.0.so.3
#11 0xb71c3c4c in g_cclosure_marshal_VOID__VOID () from /usr/lib/libgobject-2.0.so.0
#12 0xb71a7a72 in g_closure_invoke () from /usr/lib/libgobject-2.0.so.0
#13 0xb71ba8a0 in ?? () from /usr/lib/libgobject-2.0.so.0
#14 0xb71c3306 in g_signal_emit_valist () from /usr/lib/libgobject-2.0.so.0
#15 0xb71c34b2 in g_signal_emit () from /usr/lib/libgobject-2.0.so.0
#16 0xb76159d5 in gtk_widget_activate () from /usr/lib/libgtk-x11-2.0.so.0
#17 0xb74f7ce1 in gtk_menu_shell_activate_item () from /usr/lib/libgtk-x11-2.0.so.0
#18 0xb74f80ba in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#19 0xb74ec7b8 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#20 0xb74e3374 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#21 0xb71a63c7 in ?? () from /usr/lib/libgobject-2.0.so.0
#22 0xb71a7a72 in g_closure_invoke () from /usr/lib/libgobject-2.0.so.0
#23 0xb71ba6a5 in ?? () from /usr/lib/libgobject-2.0.so.0
#24 0xb71c308b in g_signal_emit_valist () from /usr/lib/libgobject-2.0.so.0
#25 0xb71c34b2 in g_signal_emit () from /usr/lib/libgobject-2.0.so.0
#26 0xb7616a76 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#27 0xb74e14ed in gtk_propagate_event () from /usr/lib/libgtk-x11-2.0.so.0
#28 0xb74e18ef in gtk_main_do_event () from /usr/lib/libgtk-x11-2.0.so.0
#29 0xb736fb3a in ?? () from /usr/lib/libgdk-x11-2.0.so.0
#30 0xb710cb72 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#31 0xb710d350 in ?? () from /usr/lib/libglib-2.0.so.0
#32 0xb710da1b in g_main_loop_run () from /usr/lib/libglib-2.0.so.0
#33 0xb74e05b9 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#34 0x0804e57d in main ()

Distribution: Arch Linux