How good of a network troubleshooter are you?

If your really good, can you answer my question? :)
I have the typical home setup: a router to the internet and internal network with various computers on it. All the internal computers can access the internet except one Linux box.
If I type `ping yahoo.com` it will resolve the IP
If I type `traceroute yahoo.com` it will start tracing the route.
When I type `wget yahoo.com` to responds 'failed:No route to host'
This box runs a web server and the router is configured to forward ports to the box. The web server will respond and work perfecty if computers connect from the outside world.
I can connect to internal machines without a problem.
If I use nmap and do a syn scan on an open internet port it declares that it is open, however if i do a tcp connect scan to the same port it declares that it is filtered.
I have replaced network cards and routers, to no avail.
I'm stumped as to what to try next. If anyone has any suggestions, I would be very greatful.

well if you scan yourself with nmap over the inet back to your box you will get bogus info! :wink:
on the wget thing i dunno i was able to wget yahoo.com's index.html

I actually have run nmap on the borked box and scanned a known good box on the internet.