Cross domain uploading for jQuery File Upload

Cross domain uploading for jQuery File Upload

I know this has been asked on SO before, but everything I've tried doesn't
seem to work...I'm using jQuery File Upload by BlueImp, and I need to do a
cross-domain upload (from sub.site.net to files.site.net)
I've looked at how to do it, and here's my headers for index.php (on the
receiving server)
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: POST, GET, OPTIONS');
header('Access-Control-Allow-Headers: *');
Looks right to me...
When I go to upload the file, I get this error:
XMLHttpRequest cannot load http://files.site.net/. Origin
http://sub.site.net is not allowed by Access-Control-Allow-Origin.
So apparently something's wrong with the headers. Can anyone help me with
this? Let me know if more info is needed...
BTW the upload folder does have write permissions. Thanks!