I get that too, I think its a bug in the code, but I havent had time to look at the source or contact the developer about it.
I'm just avoiding the problem by generating the control + menu items when the form is first loaded. Alot easyer to make changes too than with the property editor too.
VB Code:
Dim topMenu As Crownwood.Magic.Menus.MenuControl
topMenu = New Crownwood.Magic.Menus.MenuControl()
topMenu.MdiContainer = Me
Dim MenuFile As MenuCommand = New MenuCommand("&File")
Dim MenuFileOptions As MenuCommand = New MenuCommand("&Options...", ToolbarImgLst, 3, New EventHandler(AddressOf MenuFileOptions_Click))
Dim MenuFileExit As MenuCommand = New MenuCommand("E&xit", Nothing, Nothing, New EventHandler(AddressOf MenuFileExit_Click))
MenuFile.MenuCommands.AddRange(New MenuCommand() {MenuFileOptions, MenuFileExit})
Me.Controls.Add(topMenu)
For example.