This is not enough information for you to get specific troubleshooting
advice. Probably you have misconfigured your firewalls. Run the Network
Setup Wizard on both machines. Usually that is enough to solve the
issue. Make sure you are only running one firewall on each machine.
Here are some links to help walk you through setting up your network:
And here is an excellent network troubleshooter by MVP Hans-Georg
Michna. If you take the time to go through it, it will usually pinpoint
the problem area(s): http://winhlp.com/wxnet.htm