404 error when exporting entries

On our site, I get a 404 error any time I try to export form entries from this admin page:

/wp-admin/admin.php?page=gf_export

I have tried multiple forms, selecting only a single field, selecting all fields, both in FF and Chrome... No deal.

The server logs do not show any 404 errors--they show 200's every time I try to export. So I figure it must be something about how the headers are interpreted by the browser?

The most interesting part of the issues is that when I check the response that is returned, it has an HTTP 404 response code, but it does have the CSV file content in the response. Because of the 404 response code, though, the browser doesn't start the download or display the CSV content.

By adding this to line at line 14 of /wp-content/plugins/gravityforms/download.php, I am able to get the file to download properly.

header('HTTP/1.0 200 OK');

Does anyone know why that hack might be needed?

In case it helps, here are the request headers:

(Request-Line)	GET /wp-content/plugins/gravityforms/download.php?form_id=3&f=export_1283018192.csv HTTP/1.1
Host	test.plugsmart.com
User-Agent	Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8
Accept	text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language	en-us,en;q=0.5
Accept-Encoding	gzip,deflate
Accept-Charset	ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive	115
Connection	keep-alive
Referer	http://test.plugsmart.com/wp-admin/admin.php?page=gf_export
Cookie	[removed]

And the response headers:

(Status-Line)	HTTP/1.1 404 Not Found
Date	Sat, 28 Aug 2010 17:56:32 GMT
Server	Apache
X-Powered-By	PHP/5.2.14
X-Pingback	http://test.plugsmart.com/xmlrpc.php
Content-Description	File Transfer
Content-Disposition	attachment; filename=export.csv
Content-Transfer-Encoding	binary
Expires	0
Cache-Control	must-revalidate, post-check=0, pre-check=0
Pragma	public
Last-Modified	Sat, 28 Aug 2010 17:56:33 GMT
Content-Length	9
Keep-Alive	timeout=2, max=99
Connection	Keep-Alive
Content-Type	application/octet-stream

With my hack, it works, so it's not super urgent. It would be nice to know why this happened, though.

The hosting provider is DreamHost, and I think they run CentOS.