Do these steps in this order:
Use the BPS Pro built-in Upload Zip installer (NOT the WordPress Upload zip installer) to reinstall the BPS Pro zip file. You will not lose any settings – this is just reinstalling the BPS Pro files.
Upgrading|Reinstalling an existing BulletProof Security Pro Installation (Using the BPS Pro Built-in Upload Zip Installer)
http://forum.ait-pro.com/forums/topic/bulletproof-security-pro-bps-pro-upgrade-installation-methods/
If you are still seeing the php Fatal error after reinstalling the BPS Pro zip file, deactivate all of your WordPress plugins to see if the php error is being caused by another plugin that you have installed. If you are no longer seeing the php error after deactivating all of your plugins then reactivate your plugins one by one to find out which plugin is causing the issue/problem.
If you are still seeing the php Fatal error after deactivating all plugins then the php Fatal error is being caused by something on your server. Most likely a Proxy|Routing problem or a PHP configuration issue/problem in your server’s php.ini file.