Happens only to one professor when attemtping to edit course settings. Course Administration / Edit settings results in "Category not known!"
Will work correctly for other professors.
Not heard of that before ... could be a bug, but here's something to try ...
temporarily move that one course to another category - then move it back into the category it's supposed to be in.
Then, login as professor and turn editing, edit course settings.
Could also have something to do with that professors session information and/or account setup. That person a manager of that category? Check into that as well.
Professor might have to clear his/her browser cache.
'spirit of sharing', Ken