lost Internet connection

I have an old blue & white, upgraded to a G4, running Tiger. I recently ran upgrades to Tiger & Quicktime and installed one RAM chip. Everything worked fine for a few days. Last night I abruptly lost internet (& mail). I have checked modem, router, cable, etc. I can network with other computers over ethernet cable, but no internet.

Any ideas?

Hardware?

After booting from a different HD, the problem persisted. Shared a connection via firewire (would only work with cat 5 cable removed). Assume it is a problem with the ethernet card and therefore a hardware issue.

If you could network with others on your network (first post) then the ethernet card is working.

Do permissions and verify disk to start. Check to see ethernet is first in the choices Preferences>Network make sure it has a valid IP number - disable all those not used.

Is there a router connecting to the internet? Can you ping it (Applications>Utilities >Network Utility). Try unplugging the router for 15 seconds.

Perhaps the ethernet wire to the router has a broken wire in it or bad plug (loose wire inside).

Thanks for replies. When I booted from another HD, it was one with a separate OS, Safari, Mail, etc. on it. It still wouldn't connect, so it is not a software or setting problem. I replaced the cable-no help. The router is fine.

With the cat cable connected, it shows I'm connected to internet, IP address, etc. but I'm not, even though I can network over ethernet. When I switch to a shared connection via firewire everything works.

I wasn't using the computer when it went down, so I can't trace the fault actions.

I shut off the firewall, so it shouldn't be a blocked port.

The more I think about it, the broken wire problem seems to fit. Since I changed cables, it is more likely to be a pin connector on the board.