@ stefano – Do these steps below and let me know if the problem is fixed or not:
1. Go to the Security Log page and click the Delete Log button.
2. Go to the Plugin Firewall page.
3. Select the Deactivate Plugin Firewall BulletProof Radio button and click the Activate|Deactivate button.
4. Delete all of your Plugin Firewall whitelist rules out of the Plugins
Script|File Whitelist Text Area.
5. Click the Save Whitelist Data button.
6. Click the Create Firewall Master File button.
7. Select the Plugin Firewall BulletProof Mode Radio button.
8. Click the Activate|Deactivate button to activate the Plugin Firewall.
9. Set the AutoPilot Mode Cron Check Frequency to 1 minute and turn on AutoPilot Mode if it is not already turned on.
10. Check your site using http://boomproxy.com/ and click on all main website pages: contact form page, home page, login page, etc.
11. Recheck the Plugins Script|File Whitelist Text Area and you should see new Plugin Firewall whitelist rules have been created.
12. Change the AutoPilot Mode Cron Check Frequency to 15 minutes or whatever frequency time you would like to use.