Being able to do something with the other three external HD's would indicate a problem with the Buffalo.
Have you checked the permissions for that drive? It could be that you do not have the necessary permissions to do a lot with it. It would be unusual though.
The missing Drag and Drop is also disconcerting, how do you get folders and files onto the drive if you cannot drag and drop?
Is this drive new? Has it always been like this? Did you initialize it when you first attached it to the computer, whatever computer that is. We have no idea.
How much data is currently on the drive? Can you drag files and folder OFF the drive into a folder on another drive? (Not the desktop)
More information please

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