The behavior occurs only during playback - i.e. when the MythFrontend internal video player is playing a stored recording/video file.

There is "built-in" support for the Apple remote in version 0.20 of Myth. When I quit Remote Buddy and use the Apple remote, I don't get the delays/missed keys. So I now believe it is an issue with process priorities within MythFrontend - ignoring other apps in order to ensure the video player has enough resources during playback.

Thanks for your response and help with this issue. I've just now taken the question to the Myth Users' mailing list to see if there is an adjustment possible from the Myth side in order to allow a more frequent polling of Remote Buddy activity.