Unable to flush output

Hi all, Until yesterday i was running Apache/2.0.36 (Unix) mod_ssl/2.0.36 OpenSSL/0.9.6c PHP/4.2.1 and was able to flush script output to browser (using flush() ), before the script stops executing. I upgraded to Apache/2.0.40 (Unix) mod_ssl/2.0.40 OpenSSL/0.9.6g PHP/4.2.3 and on the same script/browser configuration i have to wait untill the script stops running before i can see any output. I wish to say that it is not browser-related, because i tried different browsers, tried sending spaces to browser before the actual contents (300 spces for IE) and data is not in a table. I am running Slackware 8.1 I did't find any information on how to change this behaviour up to now, so i would be thankfull for any ideas