Hi Eric,
Some more info to the problem. We have tried testing on an older machine running Windows XP & IE 8, and we are getting a similar error upon uploading smaller files (200mb). The error is similar to what I see on your support boards for the AJAX Uploader:
Flash: the upload task is interrupted! io Error #2038
The difference between the two errors we are receiving, is that the first happens straight away upon selection of the files, whereas this second version is happening during the upload.
I have checked and our web.config file for this site has already been increased to accommodate the larger uploads, so I don't believe it's a problem there:
<requestLimits maxAllowedContentLength="2147483647" />
Thanks for your help.