Post the entire error message. Also the Plugin Firewall tools have self correcting ability so do all the manual Plugin Firewall setup steps again to see if the problem is automatically corrected.
Plugin Firewall Manual Setup Steps
1. Copy and paste plugin scripts/whitelist rules to the Plugins Script|File Whitelist Text Area.
2. Click the Save Whitelist Data button.
3. Click the Create Firewall Master File button.
4. Select the Plugin Firewall BulletProof Mode Radio button.
5. Click the Activate|Deactivate button to activate the Plugin Firewall.