There are no results returned when using $all in a query even though running the same query in a client will return results. If I change it to use $in it will return results. Here is an example of a query that works:

{
"PPL.ID" :

{ "$in" : [63,942] }

,
"DUO" : true
}

Here is the one that doesn't:
{
"PPL.ID" :

{ "$all" : [63,942] }

,
"DUO" : true
}

PPL is an array of objects:
{
"ID" : integer,
"NAME" : string
}

I realize they are two different queries, but when I run the second query through another client it does return results. I included the version using "$in" to demonstrate that the query as set up in Java isn't broken. I am currently running against MongoDB version 1.6.3 on Windows.