NSClient++ Help (#1) - Trouble monitoring 2003 R2 (#860) - Message List

Hi all.

I have NSClient++ installed on 2003, 2003 R2, and 2008 R2 servers. The 2003 R2 servers are showing connection refused even though there are no network blockages, NSClient++ is properly configured, and there is no local firewall service. The nsc.ini on the 2003 R2 servers is exactly the same as the 2003 and 2008 R2 servers which are being successfully monitored. Any ideas what's wrong?