I had an interesting situation earlier today. I opened my model from the C4R platform and all seemed fine.
I activated the mange tab to review warnings however once I clicked on the manage tab, all of the menus became greyed out and inactive.
I could navigate through the project browser and change views, I just could not use any of the menu items, inlcluding Sync.
It only seems to be in this one file and it only seems to be me having the issue. Has anyone come across this before?