Forgive my ignorance but Im not sure how to contact you privately. As a side not the logs show nothing but a a warn for
[warn] 27632#0: *416839 a client request body is buffered to a temporary file /var/tmp/nginx/client_body_temp/000000056x

the access logs simply show the following on each get progress request:
[code]
192.168.1.22 - - [04/Mar/2010:15:41:16 -0500] "GET /file_upload_progress HTTP/1.1" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)" "-"
192.168.1.22 - - [04/Mar/2010:15:41:17 -0500] "GET /file_upload_progress HTTP/1.1" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)" "-"
192.168.1.22 - - [04/Mar/2010:15:41:18 -0500] "GET /file_upload_progress HTTP/1.1" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)" "-"
192.168.1.22 - - [04/Mar/2010:15:41:19 -0500] "GET /file_upload_progress HTTP/1.1" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)" "-"
192.168.1.22 - - [04/Mar/2010:15:41:21 -0500] "GET /file_upload_progress HTTP/1.1" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)" "-"
192.168.1.22 - - [04/Mar/2010:15:41:22 -0500] "GET /file_upload_progress HTTP/1.1" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)" "-"
192.168.1.22 - - [04/Mar/2010:15:41:23 -0500] "GET /file_upload_progress HTTP/1.1" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)" "-"

[/code]