Adobe Air / Flex Redirect issue



I am trying to allow user to login using Twitter on an Adobe Air/Flex mobile app.
I open a StageWebView browser and point it to:

If the user logs in successfully on the first attempt, it redirects to:
and freezes there.

The very very strange thing, is that if the user enters the incorrect login details, and then enters the correct details on the second/third attempt, it redirects successfully and everything works as expected.

Any help or guidance would be massively appreciated.

thanks very much!