Can't tab focus the file queue unless scrollbar showing, using FF3

Can't tab focus the file uploader unless the scroll bar is showing in the uploader.

Steps to reproduce:

1) Open either the inline or pop-up version of uploader from the daily build site:
http://build.fluidproject.org/fluid/sample-code/uploader/inline/index.html
http://build.fluidproject.org/fluid/sample-code/uploader/pop-up/index.html

2) Add a couple of files.

3) Tap the tab key, notice that the file queue does not get focus

4) Add some more files, so that the scroll bar appears

5) Tap the tab key, notice that the file queue is now able to get focus.

6) remove some files until the scroll bar is gone

7) Tap the tab key, notice that the file queue does not get focus