1. Go to the remote desktop server.
2. Open Task Manager and click on Processes tab.
3. Look for rdpclip.exe process.
4. If find rdpclip.exe then End Process this by right click on it.
(well if you dont find rdpclip.exe in task manager then no need to worry just follow 5th step.)
5. Go to Start>Run type “rdpclip.exe” without quotes and hit enter.
6. Now your copy/paste start working.