HELP!!! session_start() stucks the script

Hi, first allow me to thank anyone who takes part in helping and answering to any question in that mailing group, I learnt a lot just by reading the Q and A of others. I am using PHP4.0RC1 (with the zend optimizer) on WinNT and IIS. My problem is that when my script arrives to the "session_start()" function, the script simply stucks, I get the output BEFORE that function, but nothing happens after. Even HTML that I added after I closed the script didn't come out. I checked the "session.save_path" in the php.ini file and it is set on "/tmp". I understood that this means I should have "C:\tmp" in my system, I added tmp folders to any possible and reasonable place yet nothing helped... What else can be done? I know that I am not alone in that battle. Thanks in advance, David, Israel.