I have both some sample code and my app working with SWFUpload.

I have gotten through the config, and in IE it successfully selects files and displays the thumbnails in the example demos.

(I'm setting aside the Firefox cookie issue for now)

In my app, it selects the files, it does save the record and the file to the database, it does not show a thumbnail -- it gives a 500, and finally the file saved in the database does not display correctly.

So, I think there are two issues:
1. What do I need to return from the upload to the page so the thumb doesn't 500?

2. What does my upload page need to expect of the file?
My current upload code is based on my app's existing upload and modified a bit for SWFUpload. It does not error (in .net). I already changed my code so it looks at the file extension for the PostedFile's ContentType. (Since Flash sends it as "application/octet-stream").
I'm wondering if I missed something about what my uploader should need to do to use the PostedFile and make it an image that can be saved to the db. But, everything in the code looks ok to me.