I tried to remap the Zap button and direction buttons to work for Favorites on my Sony Wega TV. I get the message below. There's no "undo", I'm totally hosed.
Have to start everything over from scratch !?!?!?
Harmony, get a clue!!!! This is seriously deranged.

An Error occurred while Updating...
Error Message:
Invalid menu (VirtualTelevision_Watch Television_ModeInteractiveTv).
Context:
The name of the device, activity or sub-system that generated the error was Change Button Function

Additional Information:
The warnings listed below are not errors, they are informational only.

Warning(DVD): Empty action for ChapterNext
Warning(DVD): Empty action for ChapterPrev
Warning(DVD): Empty action for NextTrack
Warning(DVD): Empty action for PreviousTrack
Warning(Stereo Receiver): Empty action for TuningUp
Warning(Stereo Receiver): Empty action for TuningDown
Warning(PVR): Unable to simulate volume mute
Warning(PVR): Empty action for VolumeUp
Warning(PVR): Empty action for VolumeDown
Warning(PVR): Empty action for Menu
Warning(PVR): Empty action for Cancel
Context: Change Button Function

My experience has been that mapping a hard key under the Navigation section causes this error. Not sure why but it does.

OK, how do I "undo" the damage?
Try to re-remap the keys to what they were?

OK, Dan helped me out.
Just "Remove Activity".
Guess I got carried away (this can be very frustrating).

But then I see that the button activities are generically named, and I hadn't realized when I set them up that I needed to go to "Rename Activity" to know the association later.

Therefore, I had to remove ALL button activities.
When you go to rename, it doesn't tell what the button is associated with; you can just give it a new name.