This is not a DavDrive bug but a Nautilus/gvfs bug which is present for more than two years.
For more detail see the Ubuntu bug report #267642.
When copying a directory with Natilus only a file containing the directory listing is produced:
|Result of Nautilus directory copy|
The bug report mentions a workaround:
Copying directories is possible by using a shell and accessing the ~/.gvfs folder directly.
|Directory copy from Shell|
Hopefully this nasty bug will be fixed soon.