That advice might be fine for the casual Mac user, but it's not helpful nor is it good advice for a Mac user who is a designer managing fonts through apps like Suitcase, FontExplorer, etc etc, which actually TAKE PLACE of FontBook entirely.
Please be careful before advising people dig thousands of fonts (I have over 30,000) by using FontBook.
As for people getting aggravated that this discussion has several solutions, EVERYONE Is having the same error message. So it makes perfect sense that various solutions will be placed in this thread since my PROBLEM is the same as yours, but evidently the
solution isn't.