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 of 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 - wrong: it still does). See: Why does copying over RDP sometimes not work? and Can't copy and paste in Remote Desktop Connection session.
Today (19 mar 2015) it happened on Windows 7 Pro SP1 64 bit connecting to Windows Server 2003 R2 SP2. Text works, files not. Both directions.