I am using session_start() and session_id() trying to  identify visitors to my site. 
Problem: the session.cookie_lifetime is set to 0, but with IE5 the session does not expire when closing all browser windows, clearing cashe and or deleting cookies.
The session expires as expected when using NS4.

The only thing I can figure out is that IE5 isnt actually closing, but keeping the session even though I close the browser windows, but that sounds insane!

But... how can I solve this?

THE SESSION SETTINGS:
session.auto_start Off Off 
session.cache_expire 180 180 
session.cache_limiter nocache nocache 
session.cookie_domain no value no value 
session.cookie_lifetime 0 0 
session.cookie_path / / 
session.cookie_secure Off Off 
session.entropy_file no value no value 
session.entropy_length 0 0 
session.gc_maxlifetime 1440 1440 
session.gc_probability 1 1 
session.name PHPSESSID PHPSESSID 
session.referer_check no value no value 
session.save_handler files files 
session.save_path /var/php-sessions /var/php-sessions 
session.serialize_handler php php 
session.use_cookies On On