Internet is plugged into WAN port of the router?

jimasek wrote

Internet is plugged into WAN port of the router?

Yes, I have a functioing ADSL modem plugged into the WAN port, which should be clear since, as I mentioned, the internet works fine even when the router's web server no longer works. I can still access the internet from the local machines on the network. And the local machine that accepts VNC connections can be logged into remotely, so the port redirection on the router is also still working. (Actually, all of these will eventually stop working too, but that is not what I am asking about right now. This can be fixed remotely by rebooting the router, so it is not as serious when it happens. However, when the web server of the router stops working it is far worse since once cannot fix this remotely, but has to handle router physically).

Also, it clearly cannot be a problem of something plugged in incorreclty, since everything works at first. The router's web server does work at first for a while, but eventually stops working. It cannot be accessed remotely from the internet, but nor can it be accessed locally from local machines. So this is not an internet problem and it should not matter whether the modem is plugged in to the WAN port or not. The problem arises even for the local machines regardless of whether the internet is being used.

When one cannot access the web page, in short, everything else still works. Telnet to port 80 gives connection refused, rather than a stealthy no reply, so that the port is still open in the firewall as well. One can still ping the router, both over the internet and locally.