EDIT: some idiot felt he was rewriting his answer. Not. Or I will remove it. According to a reviewer who initially declined to edit: "This change is too small, the proposed changes should be significant improvements, addressing several issues in the message." So: do not.
Apple has a formal decision (where they are reluctant to accept their mistake in hardcoding the menu):
http://developer.apple.com/library/mac/#qa/qa2001/qa1289.html
It seems that you are working fine once you install IBOutlet:
@property( nonatomic, retain) IBOutlet NSMenu* fileMenu;
... , AppDelegate, MainWindow.xib(, blue-cube Object AppDelegate)... NIB app-delegate.
EDIT: , - Apple Xcode4, . :
NSInteger openDocumentMenuItemIndex = [self.fileMenu indexOfItemWithTarget:nil andAction:@selector(openDocument:)];
if (openDocumentMenuItemIndex>=0 &&
[[self.fileMenu itemAtIndex:openDocumentMenuItemIndex+1] hasSubmenu])
{
[self.fileMenu removeItemAtIndex:openDocumentMenuItemIndex+1];
}