"Connection refused" means either the server is not accepting connections on a port or that a firewall has blocked the request.
How do you connect two OS's running on the same computer through a router? Just curious. Never done it. Do they have different IP's and ethernet connections?
Can you ping from one OS to the other? That's probably the biggest question.
Are you sure you are connecting to the correct port? 80 is the default for HTTP connections but I think Tomcat listens to 8080 by default.
I don't know if the XP firewall would be the culprit, since the XP connection is outgoing, but check this out:
XP Internet Connection Firewall Depending on your Linux distribution, you may have a firewall running there too. Check your documentation.