Yes, I have downloaded the widget. It worked fine in 3.0 but i wanted to updgrade to viewer for flex 3.1 so I could take advantage of the updates of the identify widget. I updated both to 3.1 versions and it no longer appears.
Do you have any troubleshooting software such as Fiddler or Firebug running when trying to access this tool to see if it reports any error information to you?