This message occurs in the Holidays Manager, if you are trying to move a holidays set (or holidays set folder) into a location that is not compatible with the moved set or folder.
Possible reasons for this message are :
•You are trying to add a folder into a leaf. Only folders can hold other sets or folders.
•You are trying to move the Q++ root folder.
•The set or folder that you are trying to move does not belong to you. This can happen at some user sites where data is shared among more than one site, with each site having a certain part of the sets hierarchy reserved to it. This can also happen if you try to move any of the sample holidays that are included with Q++.
•You are trying to move a folder into one of its children.
•You are trying to move a leaf/set into the Q++ root folder. Only folders can be moved to the Q++ root folder.
Most of the above restrictions should be intuitive. For more immediate feedback on what move are allowed or not, try using drag and drop to move a set; depending on the set over which the cursor is, the cursor will immediately display visual feedback indicating if a move is allowed or not.