big files download with php - configuration problem

Hi all, I have a set of php scripts that handle the browsing and download of file from the server. it has worked fine for a long time on a server linux, now I have got to migrate those scripts also on a windows server, and something very strange is happening: the download process hangs when downloading big ( 50 MB and up ) files from the server, and the files are only partially downloaded. the log on the server shows a Timer_connectionidle error message. I'm quite sure it is a configuration ( php or IIS ) issue, but I have no idea about what could be the problem. it is not an execution time problem since I have set the max_execution_time on the php.in to a very large value. it seems that the php script simply stops communicating with the server, and after a while the server kills it. the original script used a readfile($filename) function, I have also tryed to replace it with fopen($filename, 'rb') and a while cicle with fread($filename, $chunksize), but with no success. the server is Windows Server 2003 with IIS. php Version is 5.2.5 any of you experienced a similar problem, or has any idea on what could be the problem? Thanks,

     Giulio

Giulio Mastrosanti giulio@cantoberon.it