 			
 			SecondaryKeyNumColumn.allKeysHack = true; // dimension slider hack
 			
-			_keys = column ? column.keys : [];
+			_keys = column ? column.keys.concat() : []; // make a copy so we know length won't change during async task
 			
 			SecondaryKeyNumColumn.allKeysHack = false; // dimension slider hack
 			

			
			_v = 0;
			_count = 2;
			
			return 1;
		}

		{
			for (; _count < _sortedValues.length + 1; _count++)
			{
				if(_m==0)
				{
					_s1= 0;
					_s2= 0;
					_w= 0;
					_m =1;			
				}
				for(; _m < _count + 1; _m++)
