Glad I could help, Strider.
Greenlaw wrote:Wes, any idea what causes that error?
This happens due to "orphaned keyframes", where the animation channel is not really registered as keyframed with a value on frame zero. Since you can't really delete a frame zero keyframe, if frame zero hasn't registered a key value, the first key seems to be considered the undeletable "anchor" key. But no idea what specific action causes this. It may be a combination of messing with frame zero in an action, hitting undo/redo (maybe multiple times) at an odd moment, or something completely different.
Copying to zero usually works for me too, but every now then I get a really stubborn keyframe. When that happens, I try a bunch of stuff like copy zero to the keyframe and then copy back to zero and then delete, or make a new keyframe and drag it over the bad one and then delete, etc.
Fortunately, this problem happens rarely but I've never understood what causes it.
Yeah, it seems fairly rare here too. Seems like I have seen where pasting it to frame zero doesn't work occasionally. If so, selecting and pasting all the keys above frame zero on the channel to frame zero seems to free it up again. I haven't found one that I haven't been able to delete, one way or another.