I checked the Feed and I do not see any 403 errors. I do see this error and the Feed is not displaying correctly: “This XML file does not appear to have any style information associated with it. The document tree is shown below.” You can do BPS troubleshooting steps #2 and #3 to eliminate that BPS is causing any problems.
http://forum.ait-pro.com/forums/topic/read-me-first-free/#bps-free-general-troubleshooting
2. On the Security Modes page, select the Deactivate Root Folder BulletProof Mode (Default Mode) Radio button and click the Activate|Deactivate button.
See Custom Code Note
3. On the Security Modes page, select the Deactivate wp-admin Folder BulletProof Mode Radio button and click the Activate|Deactivate button.
See Custom Code Note