Problems using Vector in Flex Builder 3

Question

I've been using Vector with no problems in Flash Builder Beta, but when I try the same thing in Flex Builder 3, the compiler throws a fit when I use it. 
public function PuzzleEvent(type:String, pieces:Vector.<Sprite>, bubbles:Boolean=false, cancelable:Boolean=false)
     //handle PuzzleEvent
The other strange thing is, Flex automatically adds this line when I use vector:
import __AS3__.vec.Vector;
An import shouldn't be necessary should it?  Vector is in the top level package right?  With or without that import statement, I get compile errors.  Has anyone else had such problems with vector in Flex Builder?
Dan

Answer 1

The only way I was ever able to solve this problem was to use Flex builder Beta and now Flash Builder 4.  I did target flash player 10.0.0, but I still never could get it to work.  At least it works in Flash Builder 4.