Since DB.slaveOk() is deprecated, I switched to using DB.setReadPreference(SECONDARY) instead. If I have a Mongo connection to a secondary member, and I set the ReadPreference to SECONDARY, I'm able to successfully make queries and perform other operations, but I cannot call DBCollection.count() or DBCursor.count(). In both cases, I get the same "not talking to master and retries used up" error that happens when ReadPreference isn't set correctly. If I switch back to using DB.slaveOk(), the error goes away.