 		/**
 		 * String -> index in sorted _uniqueStrings
 		 */
-		private var _uniqueStringLookup:Object;
+		private var _uniqueStringLookup:Object = new JS.Map();
 
 		public function setRecords(keys:Array, stringData:Array):void
 		{

			_asyncSort.abort();
			
			_uniqueStrings.length = 0;
			_uniqueStringLookup = {};
			_stringToNumberFunction = null;
			_numberToStringFunction = null;
			

					return _i / _uniqueStrings.length;
				
				var string:String = _uniqueStrings[_i];
				_uniqueStringLookup.set(string, _i);
				
				if (_stringToNumberFunction != null)
				{
