Question : FancyUploader Error

I'm having problems with getting FancyUploader to work (http://digitarald.de/project/fancyupload)
The problem is this:

When I load index.php in FireFox and try to upload an image I get:
Error #2038: File I/O Error. URL: https://site.com/script.php

Which is apparently passed back from the swf. However, when I switch to IE (in the same FireFox browser using IE Tab) the uploader works fine, when I switch back to FireFox the upload works fine for the rest of the session. When I open IE in it's own window it also works fine.

From what I've been reading many people say add the following to .htaccess because there is an issue with mod_security and flash sending back headers:
SecFilterEngine Off
SecFilterScanPOST Off

But when I add this I get an 500 Internal Security Error. Moreover, I don't think getting SecFilterEngine Off to work would resolve the original issue because why will the uploader work in FireFox after opening IE in the same window?
 

Answer : FancyUploader Error

this soounds like your application sends a wrong 401 response
please check with a sniffer or proxy what exactly your application sends as response through apache