If your site is having memory limit issues, you may be able to adjust this yourself – or, you may need to speak with your host. To adjust it on your own, here are some things you can try:
1. Edit your wp-config.php file.
Add this to the very bottom, right before the line that says, “Happy Blogging”:
define( 'WP_MEMORY_LIMIT', '256M' );
WordPress memory can be different from 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. Edit your PHP.ini file.
If you have access to your PHP.ini file, change the line in PHP.ini If your line shows 64M try 128M:
memory_limit = 256M ; Maximum amount of memory a script may consume
3. Edit your .htaccess file.
If you don’t have access to PHP.ini try adding this to an .htaccess file:
php_value memory_limit 256M
4. If none of the above works then you would need to talk to your host about having them increase your memory limit.