Ethernet Shield broken? Need help to troubleshoot this:

Hi all, I'm trying to make a webserver to transmit a temperature reading over ethernet. I have an Ethernet Shield with SD reader, and Arduino Uno.

I tried at first to upload the defaul WebServer sketch of the IDE: the ethernet port LED blinks, but it doesn't reply to pings or web requests, and doesn't write anything on serial port.

Can anyone help me with the troubleshooting, please? I feel lost. Am I missing something stupid?