Lost all network server capability
Recently I got a new computer and upgraded to 13.10 - my old computer didn't have a video card that was good enough for Ubuntu 13, so I bought a new System76 with 13.10 preinstalled.
Generally, everything works quite well. But now my network servers (mail and Apache, especially) don't work. I can get ssh to work, so something is getting through, but as far as Apache is concerned, I can't even get anything like a failed attempt to show up in the error log, or the access log. Nothing. The computer appears to have no idea that anyone outside requested a service.
Incidentally, Apache does work on my local LAN - both from the computer running the server, and from a laptop using wifi. But nothing comes in from the outside.
I'm not at all convinced that Ubuntu is the problem, but I don't really have a better forum to post to.
So the things that sit between my LAN and the outside world are a Netgear WNR3500L router and a Motorola SB5101U Surfboard cable modem. Both appeared to be working fine prior to the changeover to the new computer, but I can't be sure that everything was good to the last minute.
The router is configurable. I have it set for port forwarding for ports 22, 80, 443, and 8080. Everything looks fine, and as I said above, ssh (port 22) works, but Apache appears to get stopped completely. Anyway, if I am doing something wrong there, I don't see it. All I have found in the configuration that might be relevant is the port forwarding/triggering and NAT filtering, which I have turned off. There are some other WAN-type settings, but I don't see where they would be a problem.
The cable modem does not appear to be configurable. Does anyone know how to configure one of these things? I didn't find anything on the Web.
My line provider/ISP swears up and down they haven't changed anything.
Any ideas? Other plcaes to look?