Check to see if the location of the Equipment CUIx is in the support file search paths. If you (or a third party tool) is doing something funky with the Main/Enterprise CUIx system that might be preventing it from loading as partial. Don't forget about workspaces either - the CUIX could be loaded but the menu isn't part of the workspace, or the current workspace is in the Enterprise and therefore can't be modified,.

For what it's worth, I've always loaded it as partial to the Enterprise so it's available at startup, regardless of whether Equipment is loaded or not.