Tab between components

I Play With Physics Registration Form From Blog Doug Mccune

I am trying to make it so that after I have finished typing the username, I can press the tab key to go to the password field and go back to the login button. I'm a bit n00b with flex, so I assumed setting the tabIndex properties would solve this, but it doesn't.

Any ideas?

EDIT: After a little further research, the problem seems to lie with the PhysicsContainer. If the physical container is removed, then tabbing works without problems. Unfortunately, this also hits the point of the whole project