Along with this security issue, Font Book ran into corrupted fonts which I removed as noted earlier. I had also tossed my Caches and byHost folder to see if that would help.
As a side effect, Mail.app was drawing its from field on top of the subject field. Safari and OmniWeb had the wrong display font. Even though Times, a system font, showed in User A’s font book, it did not show in mine.
So on a lark I tried selecting all fonts in /System/Library/Fonts/ and did File->Open. Then I quit font book and now Mail, Safari and Omniweb are happy.