Starting from version 3.0 64MB of allowed PHP memory is mandatory for the plugin. WordPress takes 25-30 MB of memory just by itself. Plugin now supports 21 networks and it takes 5-7 MB
Using it on 32MB websites will just put your site out of memory and kill it’s performance.

If you need some technical details:

Plugin uses this function to detect the memory: $memory_limit = ini_get(‘memory_limit’);

If your server allows runtime php.ini variable changes you can try to put this to the wp-config.php file:

define( ‘WP_MEMORY_LIMIT’, ’64M’ );

Otherwise you need to change it directly in the php.ini file. Please contact your hosting provider or server admin if you don’t know how to do this.