after updating from 1.8.3 to 2.0.0, we are seeing numerous 'could not initialize cursor across all shards' reported by mongos. we have 4 shards, each a replicaset of two replicas and an arbiter. all nodes--mongos, config, replicas, & arbiters were updated to 2.0.0.

Tue Sep 27 21:19:26 [conn900] ns: my_db.my_coll could not initialize cursor across all shards because : ns: my_db.my_coll ClusteredCursor::query @ shard3/10.x.x.46:27017,10.x.x.47:27017 attempt: 5