Many folks use Dynamics GP over a Citrix or Terminal Server connection. At Dynamics GP Land, Steve Endow takes a looks at the problem of copy and paste breaking between the server and the local machine. Usually, stopping and restarting the RDPClip service will work but sometimes you just have to disconnect and reconnect.
Copy and Paste Issues in Remote Desktop
Archived post from 2010. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.