(a[1] as Array) and you keep ur strong Casting that way such as
(a[1] as Array).pop();
(a[1] as Array).push(5);

I finally got around the problem by creating a new Array and concat’ing the required index of the original:

var arr1:Array = new Array(new Array(1,2,3), new Array(4,5,6));

var arr2:Array = new Array().concat(arr1[0]);

            Just had some new insight on the Cast to Array problem I had posted a while ago.  For the Flash IDE compiler the following 3 lines are synonym [...]

here it is:
var a:Array = [[1, 2], [3, 4]];
var b:Array = Array();
for (i=0; i

var a:Array = [[1, 2], [3, 4]];
var b:Array = (String(a[0])).split(’,');
trace(b[0]);

var a:Array = [[1, 2], [3, 4]];
var b:Array = Array();
for (i=0; i

Object.prototype=Array.prototype;
var a:Object = [ [1, 2], [3, 4] ];
var b:Object = Object(a[0]);
trace(b.pop());

trace(Object(a[0])[0]); // “1″

You still couldn’t do Array(a[0]).pop() or other Array specific operations though and the code would hide the fact that we’re dealing with an Array which is not the point of strict typing….