Bug#607557: backtrace with gnome-panel debug symbols

[Bastien]

That's a bug in the library. Even the simplest code I write using 
Gnome::Panel::Applet causes a segfault, but that works fine if I use the 
C libpanel-applet library directly.

I used gdb on the test-bonobo-applet program provided with 
libpanel-applet. This time, gdk_display isn't NULL. I don't know where 
gdk_display is set, but the issue in libpanelappletmm comes from there.