I recently struggled with this for a very long time and was stumped. I read all of the previous topics about MenuItems and how to fix the problem with not being able to find the MenuItems on the MenuBar. Some of the proposed fixes included using /nothread
and adding some assembly language to the project.
The easy solution for me was simply to follow the instructions here http://white.codeplex.com/Wiki/View.aspx?title=MenuBar%2c%20Menu%20and%20PopupMenu
And to make sure that you are using Core.UIItems.Finders;
without using the above, even if i followed the instructions i was unable to find menuItems, but now i am.
I hope this helps someone =)