Ethernet Jack Not Working

I don't know if it is a coincidence that I recently upgraded to Snow Leopard, but my computer is not recognizing a connection when an ethernet cord is plugged in. I know the connection is valid because the internet company has checked the connection, and it is working fine with my AirPort Express... just not directly into my computer. Any advice??

Try another ethernet cable and another ethernet jack if possible. Ethernet cable connectors are easily damaged so be sure to check both ends. Best to use a new cable as a test.

Regards.

I have tried another cable, and other outlets and still have no connection; the Network Diagnostics say "cable is unplugged" even though the same cable connects to my AirPort /

That leaves either the ethernet input connector or the ethernet controller in your machine that may be defective. Go to Applications, Utilities, and open your System Profiler application. Click on "Ethernet Cards" and see if it lists both your Airport card and ethernet controller card.

If the ethernet controller card is listed, run the Apple Hardware Test using your install media. Here's a LINK to instructions on how to run the AHT.

The Apple Hardware Test is not exactly the best test for certain types of hardware failure, but it sometimes will pick up on an airport card or ethernet controller that's bad.

Regards.

Ethernet pins tend to get dust and lint between them, causing disruptions in the connection. If you think this might be your problem, shell out 10 bucks for a can of compressed air.

Thanks for all of the help! Looks like my Ethernet card is not in Utilities... what now?