I can see the issue.
there's something on a file called superfish.js (which is responsible for rendering the menu, it looks) that's crashing and that's why you don't see the menu.
I think it's possible it could be related to jQuery being loaded twice in the page (once by your menu builder and the other by calendar planner)

to really check if this is the issue, and solve it, I would need to have FTP access to the site. can you provide it? (you can send it at support@ joomlathat.com)

Thanks for looking. I figured it might be something like this.
Could it be a future option to toggle off the loading of JQuery within the component if its already present via the template?

I'll email you.

Thanks

Actually my template gives me quite a few options in settings about what scripts load.

See grab. Perhaps I could block the CP JQuery load via this interface?

You may have noticed that my 3rd party booking form (Big green button 'Book a meeting') which uses a lightbox js is misbehaving on this CP page as well. Another script conflict.

please email me FTP and joomla access, it's the only way I can check everything.