Also, the VirtualBox's vrdp!=Windows rdp 100%.
Remember, in Windows there is a whole different environment you are working. Dragging-dropping from Linux through vdrp/rdp doesnt work (either to VBox vrdp nor Windows native rdp - but you can export a shared folder to native Windows (not VBox) through tsclient).
There are some limitations in Linux's vrdp: I used virtual machines in Virtualbox (and administered Windows machines via rdp) for quitesome time from Ubuntu/Debian.