I encountered the (most likely) same strange behaviour as another user, but I'm quite certain, it has something to do with an update to Ubuntu itself within the last week or two.
What have I done? - Used Eclipse 3.7 (Indigo) within 11.10 for month, the menu showed up - as predicted - as a seperate menu, not a global one - My own RCP application is successfully showing a global menu.
An update occured... - The menu vanished. Neither UBUNTU_MENUPROXY nor APPMENU_DISPLAY_BOTH is helping - Even tried this one - but to no avail
So until now the information I can provide is not very helpful, but starting Eclispe from console and watching the start of my own applications, I've recognized some new DEBUG messages:
** Message: a new manager occured at org.globalmenu.manager, :1.6 ** (Eclipse:16040): DEBUG: gtk-menubar-gtk2.vala:25: map called
By the way: My own Eclipse RCP applications, still working perfectly (ok, as good as I've programmed them and that might be far from perfect).`
The following lines also appear during the startup of my app
** Message: a new manager occured at org.globalmenu.manager, :1.6 ** (SWT:21632): DEBUG: gtk-menubar-gtk2.vala:25: map called ** (SWT:21632): DEBUG: gtk-menubar-gtk2.vala:25: map called
but they don't seem to have any negative effect. There is also a syserr call on exiting the RCP app:
(SWT:21632): LIBDBUSMENU-GTK-CRITICAL **: watch_submenu: assertion `GTK_IS_MENU_SHELL(menu)' failed
but this is "old news" and I never encountered any sideeffects with this.