How do I restore remote access to network was using mail.server.co.nz.

This has been working fine for some time. I believe there were some security updates and it stopped after this.
The server is a windows 2003. The policies dont appear to have changed?
Using remote desktop connection. The error is the computer can not connect to the remote compter. Remote desktop can not find the remote computer. try the computer name or the ip address again then try connecting….
Any info on how to restore this would be great.
Thanks