Under System 6, this condition is usually caused by the omission of the DA
Handler file from the System Folder. Sometimes the file is there, but it is
corrupted. Try replacing it by reinstalling System software.
If this situation happens while under System 7, try restarting the Mac and
hold down the Shift key as it starts back up. This will keep any extensions
from loading that may be conflicting with the actions you are taking. If this
doesn't work, consider reinstalling the system software.