In a new computer so far with no HD, I fail to get a connection to Internet.

The machine uses an AMD Sempron 2500 microprocessor and an MSI Motherboard Model K8T Neo-V. It has an integrated ethernet connection (eth0) but I also tested with an ethernet PCI card (eth1). I tried both with Knoppix 5.0 and 4.0 (also olders) with the same results. I use a Cisco model 677 ADSL modem.

The machine sees both eth0 and eth1, but can't find the concentrator. However, in the modem the LAN LNK green led is on, as soon as the computer is on. The LAN ACT led is off. While searching for the concentrator on eth0, the WAN and LAN ACT leds flash briefly and then go back to off. On eth1 this doesn't happen. The message on the console is 4 times "Timeout waiting for PADO packets"

With the same elements, cables and CDs, other machines work properly.

What can I do?