Hi 9566317,
I can only be of general help, as I don't have your controller type.
If in doubt, slow down your Baud setting to the lowest for testing. Use a short (shielded) cable for the test, too. Some controllers will not DNC as fast as they can upload or download, because of the handshaking requirements of DNC.
What software are you using for DNC? If you want to test drive something else, there is a link on this page for a free working copy of NCLink.
http://www.onecnc.net/download_usa/downloads_usa.htm