session-problem

hi got a big session-problem and i have no idea what i'm doing wrong... i have quite a big web-app and i tried to upgrade the code. ex: $frm_id to $_POST['frm_id'] and $HTTP_SESSION_VAR['myId'] to $_SESSION['myId'] ... ect... i changed the register_globals = Off in the php.ini and tried to browse my webapp. now my problem: i wrote in my navigation-frame this code: <?php if( !isset($_SESSION['testint'] ) ) { $_SESSION['testint'] = 1; } $_SESSION['testint']++; print_r($_SESSION); ?> after the print_r() i can see my 'testint'-session-variable on the navigation-site. however on the other frame-site. i do NOT see this 'testint'-session-variable when i reload it. and when i reload the navigation-frame the variable does appear but does NOT increase. isset() always return false!!! when i take a look at the session-file on my Computer, i do NOT find the variable 'testint'... now when i make a complete new dummy php-file and copy-paste this session-code on the navigation-site then the session works perfectly. even when i call the navigation-site again AFTER processing this dummy-php-file. the session for this variable works suddenly. what am i doing wrong??? please give me a hint! regards, jazper