I was searching for a multiple file uploader and took what you did with the single file upload for Flex and made it a multiple file uploader with progress bar, etc..
Works beautifully. You can see the files upload and if there are bigger files you can see the progress and not start clicking around thinking it's not working, etc... screen refreshes and resets the upload control and the previously selected files are now links in their appropriate section. All is good until ......
.... being so excited about my first new "Flex" app and having the ability to upload multiple files at once .. I had a Co-worker with Firefox on Mac (who is the Flex expert for our development team) try it and he promptly returned an email stating "Error" in your progress status and nothing uploaded.
What a let down.
Since, I've tried with Chrome and Firefox on a pc and still can't get it to work. I've been seeing others saying it was an authentication issue and Flash player doesn't maintain your existing website session, so if an authenticated session is required to access the template that accepts the uploaded file(s), the web server refuses access, and thus uploads won't work.
I've been looking at trying to pass the sessionID from the cookie being set when the user authenticates but ran accross this article before figuring it out.
I would love to find a solution to this as well as there are a few hundred Sales Reps that are waiting patiently on a multiple file uploader for our domino application.