When you drag a file around in the project explorer (left view), there is a visable line of where you can drop the file, these makes the cursor turn into a cross and you cannot place your file there.
You can however drag a file on top of another file insinuating that this will replace the file, this in fact places the dragged file into that folder.
This seems like very strange and unconventional behaviour.
In older versions this behaviour was in place.