I don't run gnome-panel normally. Most menubars work correctly. However, with wxMaxima and Audacity, they are not showing. When I start gnome-panel and add an appmenu, I can see the menus again.
Without panel:


With panel:


I get no relevant errors when I run from a terminal.
Why does this happen and what could I do to fix it? Against which package would I file this if this is a bug?