Force download help.

[listenmirndt]

I am using this code :
header("Content-type: application/ZIP\n");
header("Content-disposition: attachment;filename=$file\n");
readfile($filelocation);

And it works great on many servers. But on this server I am trying to get it working on now, instead of downloading the file it just downloads a 4kb empty file.

Any ideas why? Itd definatly a server configuration issue.. but I dont know what.

Thanks
-Arron