Using Mac OS X 12.6.8 and Remote Desktop 10.9.2. Beginning two versions back (10.9.0?), copy and paste works for a while after launching RD, but it eventually fails when copying from the remote mach...
I have been experiencing this issue for almost 2 years already, the only way I have found to restore the ability to copy-paste is by copy-pasting from the remote desktop to the remote desktop, and then trying to use this function from outside to inside the remote desktop (or the inverse). Not sure if this is exactly the same issue, but I think it is worth a try.