Open two ROX filer windows (or anything else that supports DnD). Rox is an easy testbed.

Try to drag a file from one of the windows to the other window - no go.

Move the window the file is being dragged to, then try dragging the file again - notice it working.

The exact way this behaves is hard to explain, since sometimes one of the windows accepts the drag while dragging the other way does not work. In any case, playing around with the receiving windows placement and size fixes the problem and the drag is accepted. Windows are being initially placed by the "Smart" placement model in my tests, but I'm not entirely sure if that is the only case this happens in.

   [pekwm: version GIT Built on Sun Jul  6 18:53:04 EEST 2008]

   PlaceNew = "True"
   FocusNew = "False" /* default was true */
   Placement {
    Model = "CenteredOnParent Smart MouseNotUnder"
    Smart {
     Row = "True"
     TopToBottom = "True"
     LeftToRight = "True"
     OffsetX = "0"
     OffsetY = "0"
    }
   }