You CAN'T see any menus there. That's the Ribbon in a collapsed state (little arrow at the far right of that row).
Use the CUI editor, check the current workspace and see if Menus are turned off (likely the case).
Check the setting for autosaving changes to workspaces. I keep it off, as if a partial CUIx cannot be found or some other problems, it will overwrite the stored workspace with the new settings.
By "loading a CUIx" do you mean you made it the Main? Or did you load it partial to the Main or Enterprise? Replacing the Main CUIx will remove all the content - including the active workspace if it's stored there.
The CUIx system takes a bit of getting used to, granted. And the editor has some quirks. But I really do like it better than the old system. There's the Main CUIx - that's typically for the user. They have full read-write priviledges to that, so it's good for per-user workspaces, plus personal toolbars, etc. The Enterprise CUIx is typically for company-level stuff. It's read-only by design so there's no accidental modification, even if the file is in a read-write folder. Good for base template workspaces users can start with, or resort to if they bugger up their own badly enough. Under the Main and Enterprise, each can have Partially loaded CUIx files to add additional content. For example, I load up the AutoCAD, Express, and Raster Design CUIx files partial to our Enterprise. We don't have any partials to the Main but it can be done by users if they feel like it.
Commands in the CUIx system are remarkably similar to XREFs. You define it once (name, command-line macro, small and/or large icon) and reference it in multiple places (toolbars, menus, Ribbon). Need to change the macro? Change the command definition and everything follows.