Description of problem:
Logged out of LXDE and logged into Xfce. After a few seconds in Xfce the failure notice appeared.  Fresh Install, first time logging onto either desktop.

Version-Release number of selected component:
lxpanel-0.5.12-1.fc17

Additional info:
backtrace_rating: 3
cmdline:        lxpanel --profile LXDE
executable:     /usr/bin/lxpanel
kernel:         3.8.4-102.fc17.i686.PAE
uid:            1000
ureports_counter: 1
xsession_errors: 

Truncated backtrace:
Thread no. 1 (9 frames)
 #0 ??
 #6 do_theme_change at gtkicontheme.c:635
 #7 update_current_theme at gtkicontheme.c:439
 #8 g_cclosure_marshal_VOID__PARAM at gmarshal.c:1042
 #14 g_object_notify_by_spec_internal at gobject.c:1133
 #15 g_object_notify at gobject.c:1175
 #16 _gtk_settings_handle_event at gtksettings.c:1988
 #17 gtk_main_do_event at gtkmain.c:1500
 #23 gtk_main at gtkmain.c:1257