Not sure I remember how this works at Bluehost, but php.ini variables aren't necessarily recursive. In other words, if you have multiple php.ini files for multiple directories or domains, you may have to change the max_file_size variable for any or all of them that may effect the directories that contain them.
Also, if you have a WordPress blog, then you can add the following to your wp-config.php file and it will take precedence over the php.ini setting...
Code:
define('WP_MEMORY_LIMIT', '64M');
Good luck!