This is the 2nd time I see such message, and I think it must be a bogus signal in gabble. Unfortunately I have no idea how to reproduce, it may be related to suspend+resume my latop while account was online.
Note that this is with only 1 gtalk account configured, and it has only 27 contacts in its roster.
tp-qt4 0.5.10 DEBUG: Got ContactList.ContactsChanged with 26 changes and 176 removals
tp-qt4 0.5.10 WARN: Contact "email@example.com" removed from ContactList but not cached, ignoring.
tp-qt4 0.5.10 WARN: Unable to find removed contact with handle 6
(last line repeated with various handles)