Originally Posted by JSanders
Have you recently updated your Windows Live Messenger, AIM or Yahoo Messenger apps?
If so, delete both or the one of those applications you upgraded, and you address book should return normal. It's a known glitch with those upgrades last week and I've been told that RIM is investigating and fixing.
Tried it again last night. You were right! You need to delete all IM programs. Windows live, AIM, Yahoo, Google Talk etc...