You should not share the repository. This will cause a lot of problems for you. Really the best plan is to protect the repository directory so that it only has access from the cvs server, plus any administrative access required for backups etc.
The pserver method uses IP port 2401. This works flawlessly for me. My guess is that you have a firewall issue where port 2401 is blocked somewhere in your network. This port blocking can occur in a number of places: on the machine itself, on the 'other' computer or on any network firewall between the 2 computers. You will need to look at firewall logs to see where the blockage occurs.
Also, you can test the connection by a much simpler method. Simply ask for version:
cvs version
This should give you the version of cvs/cvsnt on your local machine and on the server.