I have a problem with my configuration memory wordpress,

I have a problem with my configuration memory wordpress, every time I get:

Fatal error: Allowed memory size of 67108864 bytes exhausted (tried to allocate 7680 bytes) in /home/xxxxx/public_html/wp-content/plugins/wpmu-dev-facebook/lib/class_wdfb_options_registry.php on line 34

I have configured: php.ini, .htaccess, default-constants.php, wp-settings.php, wp-config.php