Undo a matrix

Question

I need to have an undo redo in my app for when the user scales or rotates an sprite. I tried to achieve the undo by doing the following:
newChanedMatrix = matrixPassedOverAfterRotationAndScaleOnASprite;
undoMatrix = newChanedMatrix.clone();
undoMatrix.invert();
to perform undo
sprite.transform.matrix = undoMatrix;
When I try this the sprite ends up about about 300 pixels north ( -y 300 pixels). And nothing happens to the rotation ans scale stays rotated and scaled.
TIA, J

Answer 1

Not much code to show.  Just download the Senocular Transform tool and put it in a Flex project, transform an object and then sit wondering how to undo it. Mediator references are to PureMVC.
public function shouldCreateTransformToolInVisMaskOverSprite(targ:DisplayObject):void
            if(!tool && targ)
                _targ = targ;
                tool = new TransformTool();
                tool.moveEnabled = false;
                tool.skewEnabled = false;
                tool.registrationEnabled = false;
                tool.constrainScale = true;
                tool.maxScaleX = 2;
                tool.maxScaleY = 2;
                tool.controlSize = 8;
                tool.livePreview = true;
                //tool.scaleWithRegistration = scale_registration.selected;
                _bigMediator.vis.marks.addChild(tool);
                tool.x = _targ.x;
                tool.y = _targ.y;
                tool.target = _targ;
            }else if( targ ){ // if tool was created previously we just reassign target and move over new target.
                shouldRemoveTransformToolFromVisMaskCompletely( false );
                tool.target = null;
                _targ = targ;
                tool.x = _targ.x;
                tool.y = _targ.y;
                tool.raiseNewTargets = true;
                tool.target = _targ;
            }else{
                // do nothing as we need a targ
                return;
            if( tool && _targ)
                tool.maintainControlForm = true;
                _targ.addEventListener( Event.ENTER_FRAME,
                                            function():void{
                                                if(tool && _targ){
                                                    tool.x = _targ.x;
                                                    tool.y = _targ.y;
                                                    tool.controlSize = 8;
                                                    //if(tool.maintainControlForm == true) { tool.draw() };
                                            }, false, 1000 );
                tool.addEventListener( MouseEvent.MOUSE_DOWN, function(e:Event):void {
                                                                e.stopImmediatePropagation();
                // This listens for when mouse is released to capture stat of targs Matrix and the state of tool Matrix.
                tool.addEventListener( TransformTool.CONTROL_UP, handleTransformEvent );