My vote goes to the router as being the culprit.
Try this. Hook your PC directly to the DSL modem and then try accessing it externally. If that works, then it confirms that the router is the issue. If it doesn't work, you need to get in touch with the DSL technical support to find out why they are blocking the request.
If the router is the issue, then you need to recheck the router's configuration, especially the firewall. I know that the router I have came out of the box with the firewall set to block all incoming requests.
thanks peter! even my dsl router does port forwarding, but no matter how i configure things i can't get port 8080 requests through. i read somewhere else on the web that sometimes ISPs block arbitrarily high port numbers - maybe that is what is happening.
rather than fight it, i just changed jboss to run on port 80 since i know those requests go through. seems to be working now.
thanks for the suggestion - it definitely helped me narrow it down.