WP-Filebase Pro needs the NONCE_SALT constant for secure server activation requests.

If you get a warning like:

Warning: constant() [function.constant]: Couldn't find constant NONCE_SALT in .../wp-content/plugins/wp-filebase-pro/classes/AdminLite.php on line 131

NONCE_SALT is missing in wp-config.php.
To fix this, add this line to your wp-config.php:

define( 'NONCE_SALT', 'put some random characters here' );

You can also generate all salts here. Just insert this code block into wp-config.php.