OS X 10.6.8/TextEdit 1.6
Out of the blue, I can toggle command-B on, but not off, in both plain and rich text documents using Lucida Fax; Arial, Helvetica, Verdana, and several other fonts I've tried work fine.
Command-I and command-U work fine, and all three options work in Mail.app.
I trashed ~/Library/Preferences/com.apple.TextEdit.plist and ~/Library/Caches/com.apple.TextEdit with no joy, and ultimately trashed TextEdit and all its appurtenances and re-installed with Pacifist, and still no joy!
The issue disappears in my test user account, but Lucida was disabled and couldn't be tested in a Safe Boot.
Is there some cache or plist that I haven't thought of?