I have just tried to add something to a folder on a drive, it shows a message of "folder cannot be modified"? I did not do anything to that drive or folder, all other 3 drives have no issue like this, it is not my main drive,it is an external. Drive has a lot of space left on it. What might have changed? I can drag and drop from folder, but not to it. I am using a G5 PPC, Dual 2.0, Leopard 10.5.2.