I use Remote Desktop from a Window 8.1 Pro 64 bit PC to a remote Windows XP Pro SP3.
Recently I noticed copy&paste of files does not work in either direction.
Copy&paste if text and images (from/to MS Paint) works fine (in both directions).
The trick with restarting rdpclip.exe does not help (note: rdpclip.exe is only on XP, I think it does not exist on Windows since Vista). See: Why does copying over RDP sometimes not work? and Can't copy and paste in Remote Desktop Connection session.