problem with menu on inherited form

If I inherit from a form that has a MainMenu, then add a
new MenuItem on the inherited form, the designer can't
seem to place it correctly after a build. For example...

Parent form menu:

File Edit Window Help

Child form menu:

File Edit Tools Window Help

After building the solution, the child form menu (in the
designer) is:

File Edit Window Tools Help

but it remains correctly placed at runtime. Is this a bug,
or am I missing something?

TIA,
Lynn Curtner