Increasing the WordPress Memory Limit
1. Edit your wp-config.php file and enter something like:
define('WP_MEMORY_LIMIT', '96M');
WordPress memory can be different to the server – you need to set this regardless of server memory settings
http://codex.wordpress.org/Editing_wp-config.php#Increasing_memory_allocated_to_PHP
2. If you have access to your PHP.ini file, change the line in PHP.ini
If your line shows 32M try 64M:
memory_limit = 64M ; Maximum amount of memory a script may consume (64MB)
3. If you don’t have access to PHP.ini try adding this to an .htaccess file:
php_value memory_limit 64M
4. If none of the above works then talk to your host.