sessions doesn't work with cookies

Hi everybody, I encounter the strange effect that the session management doesn't work with cookies enabled: As long as I am pressing the reload button at the user client the sessions get restored perfectly. But when it comes to clicking on a link with exactly the same URL as destination a new session will be started. The cookies themselfes get transmitted though, at least I can read the $PHPSESSID variable before session_start () - at this time it's content matches the old session ID. After session_start(), it still holds the same value, but SID and session_id() result a new session ID and all registered variables are destroyed :-( Funny thing: All this stuff worked before wit the same release of PHP4 but a different apache (1.3.11 with SSL-patch) on another machine (there were other problems though). Now I am using apache 1.3.12 with the SSL-patch 1.41 and PHP 4.0.1pl2. I also tried PHP 4.0.2 and 4.03pl1. Also, when I disable cookies in the php.ini file the variable SID will not be set but remain empty. To cut a long story short: the behaviour of the session management is not transparent at all. Does anybody experienced such a behaviour before? Thanks a lot. Ralf