Bug#285497: Seems related to Exchange connector.

[Mattias Eriksson]

I get this addressbook is offline when I have the exchange connector
enabled. If I disable the exchange account everything works ok. 
I suggest that the contact-lookup-applet continues to use the
addressbooks that works and just ignore the exchange addressbook. Well
the best solution would be to support exchange addressbooks, but the
exchange connector seems to be a special piece of software from what I
understand.

//Snaggen