Problem when trying to bulk insert in Casbah

File.scala

    // recurse through each element of "docs", using `builder` to add another key-value MongoDBObject for time-stamp purposes
    def getEnrichedDocs(docs: List[DBObject]) : List[DBObject] =  {
      def go(list : List[DBObject], docs_: List[DBObject]) : List[DBObject] = list match {
        case x :: xs => var builder = MongoDBObject()
                        builder = builder ++ MongoDBObject("LoadTimestamp" -> Utils.getTimestamp) // returns a Long (I know that I should be using a BSON TS, but that's a TODO
                        builder = builder ++ x
                        go(xs, docs_ :+ builder) // call go() recursively with the updated accumulator (2nd arg) 
        case Nil => docs_
        }
        go(docs, List[DBObject]())
    }

    val allDocs: List[DBObject] = getEnrichedDocs(getDocsList()) // getDocsList() unspecified here sincecontent not imp here

	// Bulk insert 
    val docsList = MongoDBList(allDocs: _*) // avoid using a List of lists 
    collection.insert(docsList) 

Also posted here - http://stackoverflow.com/questions/19058990/java-lang-illegalargumentexception-basicbsonlist-can-only-work-with-numeric-key