\Driver\Builders\QueryBuilder.cs(1015):
public QueryConditionList In(IEnumerable<BsonValue> values)

It calls `if (values.Contains(null)) ...` with a null argument. At the same time in

\Bson\ObjectModel\BsonArray.cs(648):
public bool Contains(BsonValue value)

.. there is:
if (value == null)
{
throw new ArgumentNullException("value");
}

Thus, `In` seems to be always throwing an exception in 1.4.1