If you can narrow down the plugin that is needing the extra memory you can add this line:
ini_set(‘memory_limit’, ’16M’);
to the php file for the plugin. If at first it doesn’t work, increase it by 8M until you no longer recieve the error message.
The advantage of this method is that you have more control and set this value just where you know it is really needed. Also it can be done without having access to the system php.ini, and will become active immediately.