This has been an recurring problem for me.
I have a modem/router with 4 port and after 2-3 years it would only accept the my PC connection. Meaning, any port where I plug my desktop pc it works, anywhere I plug the other devices (wdtv, wireless) don't.
These are the modem that had the same "choosy-port-syndrome"
(old) Dynalink RTA1025w
(recent) Linksys AG241
Things that I've tried are
1. power up /power down
2. swap network cables
3. resetting the router
None seems to work, it always exhibits the same behaviour which is it only accepts my PC connection. I tried googling for answers but seem to lead nowhere, i only found 1 forum comment that made sense. Basically, he reckons that the "switching" circuit that does the round robin between the routers got fried.
That did make sense a little. But if I don't plug in the PC and just plug in wireless it still doesn't work.
Currently, my modem router is Linksys AG241 (choosy port) + wireless WRP400
I'm a DB admin by trade, so setting up a home network is not too much of a hassle for me.