ok. You might try some of the other ways around that like adding the line to wp-config.php file. Theres some tutorials on the web if you'd like to try, however results are spotty on whether or not it has any effect.
You might try ssh or ftp to the server to see if you can access /web/conf/php5.ini I'm wondering if that's local on all the shared sites. make sure and back up the file first!
tim