If you need to change your PHP memory limit due to a plugin that requires higher limits. This is what you need to do.
Edit your wp-config.php file and enter something like:
WordPress memory can be different from the server – you need to set this regardless of server memory settings – Increasing_memory_allocated_to_PHP
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)
If you don’t have access to PHP.ini try adding this to a .htaccess file:
php_value memory_limit 64M
If none of the above works then talk to your host provider.