Response.write only works IE for ASP.NET

I am using uploadify ( http://www.uploadify.com/ ) to upload videos to my site and then convert them to * .flv using ffmpeg and play the preview. But it doesn't work completely with firefox, chrome or safari.

uploadify provides an onComplete interface, so when script (.ashx, .php) is used in your site to save uploaded files. you can use response.write ("blabla") or (echo "blabla") to call a javascript function that is registered as OnComplete.

I have a test with multiple video files like avi, mpg, mp4, they are less than 50MB and they all worked with all 4 browsers. However, when I tried to download a 75MB mp4 file it worked in IE but didn't work in the other three. I can see that the .flv file was created in the download folder, I can see the output of debugg messsage after response.write ("blabla"), but the javascript function was not called. those. the preview did not play.

does anyone know why? is there a timeout or something on response.write so that after a while it won't work? for example 75mb file took longer to convert than other smaller file I tried.

thansk