Diagnosis
You want to change the hierarchy in collective processing (for example,insert, delete, or move nodes). However, the hierarchy has been changedin the meantime (in a different session/window). That is why you werenot able to carry out the action.

System Response
Your change was not made. The system has, however, loaded thecurrent status of the hierarchy and is now displaying it, meaning it isnow possible for you to carry out the action.

Procedure
Carry out the action now in the updated hierarchy.