strange OSX behaviour

I wanted to reorganize my “Drop your Download here”-Drive today… but I was unable to move some of the folders. And I figured out why: You know that “last visited”-Feature of the generic OSX “Open file”-dialog. So here’s one:

As you can see, there’s the “multiplicity” folder. But who would expect that OSX will defend this folder with everything it has. Because when I try to move the folder I get the “indentify” dialog.

No problem. But when I authenticate myself it fails anyway…. So I am unable to move or delete that particulat folder. ;-(