Identify Widget version 3.0.1f for FlexViewer 3.0 : Compiler Error 1046.

Hi I am trying to compile Identify widget version 3.0 on flash builder 4.6 . however after adding the identify folder(as down loaded from http://www.arcgis.com/home/item.html...728c50461a1a89. i recieved an compiler error:
1046:type was not found or was not a compile -time constant:Popupinfo

What is remedy, how to compile it . i have used the method as defined in the Readme file of the widget.

regards
nadeem