From the BAOF manual: "Check the Enable Extended Features box if you want Backup Agent for Open Files to send logging information and alerts to the ARCserve event system. You can do this only if you are using ARCserve as your backup client, and have not enabled any other entries in the Client list (apart from remote clients). If you check the box while other clients are selected, you will be asked if you wish to disable them". See the Backup Agent for Open Files Manual for more details.
From a newsgroup post: "The error occurred when running a backup using BrightStor ARCserve Backup v9 (+ open file agent). To solve it go to the Configuration\clients on the BAOF console... uncheck the option" Enable Extended Features" and restart services."