I followed this instructions:
1. Try adding this line to your wp-config.php file:
define(‘WP_MEMORY_LIMIT’, ’64M’);
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)
My hosting provider told me to create php.ini in wp-admin directory.