I would like to know the details about un error occurred when a `count` request is given to the sharded collections like below.

mongos:[2.0.1] > db.external_data.find({user_id: 8, checked_at: {$gte: 1320211921, $lte: 1320211421}}).count()
Tue Nov 22 20:36:33 uncaught exception: count failed: {
        "assertion" : "assertion s/commands_public.cpp:445",
        "errmsg" : "db assertion failure",
        "ok" : 0
}

It seems like this error occurs when `lte` is order than `gte`.
In this case the `count` request returns 0 or this error arbitrarily even if the query is not different.

// I get this error specially via mongoshell.

Regards,