Hi,
I'm getting the same problem in Terragen 4, in fact I've seen this before but the "original" geo was hidden below ground so wasn't an issue. Has anyone found a way to fix this?
To reiterate the issue. I have a large tree population which renders fine until it is cached, at which point the original tree geo (that which is being referenced by the instances) suddenly joins in and renders at the origin of the scene. In my current project that happens to be right in the middle of the action, so is somewhat intrusive.