I've been meaning to share this for a while. I've had this show up numerous times recently. Sometimes you'll see it in the Lotus Notes client, but I've been seeing it in the server log most frequently.
The error is: 'Cannot find external name:' followed by a name in capital letters.
This is an error that is a result of having an agent signed by one ID file and an included script library signed by a different ID, usually the server ID.
The solution? Resign both elements with the same ID.