I don't use the course designer and I hate to see error messages like this. Does Microsoft ever get back to you with why the error message was thrown and if a solution is known. Trying to inject a little levity as I'm sure this leads to frustration.
In all my years with microsoft products I have NEVER gotten a response back. Those messages are their placebo effect. Something to make you feel good like they really care. BULLSH*T...!!!!!!!!!!!!!!!!
Sage.......
If there is one thing ................ummmmmmmm.......I can't remember.