Acceptance Criteria:

Show a graphical progress bar for each file upload in the file upload UI (done)
Indicate pending, in progress, complete or error states. (done)
Display a brief error message or "reason why" when errors occur.
Display "percent complete" if possible. For large files, display factional percent complete.
Upload files one at a time (serially) or limit concurrent uploads to max of 5 at a time.
Disable Browse and Upload buttons when upload is in progress.
Disable Upload button until files have been selected.
Allow a particular file upload to be "cancelled"
Allow cancel of entire upload request.

Note: if possible, when cancelling from the file browser dialog, no change should be made the current file set.