I'm having trouble to connect my Ubuntu 11.10 to internet through ethernet. I installed a router to get Wi-Fi and now (by a wired connection) I can't have internet with ubuntu (but I can with Windows 7). I see several attempts per minute of the network-manager to get a connection, but after a minute it stops trying. Here are a couple of outputs from key files:

cat /etc/network/interfaces

auto lo
iface lo inet loopback

and

ifconfig -a

eth0      Link encap:Ethernet  HWaddr 00:16:76:e4:a6:e8  
          inet6 addr: fe80::216:76ff:fee4:a6e8/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:117 dropped:0 overruns:0 frame:117
          TX packets:50 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:12221 (12.2 KB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:582 errors:0 dropped:0 overruns:0 frame:0
          TX packets:582 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:46024 (46.0 KB)  TX bytes:46024 (46.0 KB)

I tried reconnecting the modem and the router and reconnecting the ethernet cable but nothing... I tried other solutions from other posts (this one has a similar issue Wired connection not working) but again nothing. My IP is dynamic.

A couple of things I see and did:

• I see no inet addr, only inet6. I ignored ipv6 from the internet connections, and restarted the network-manager service and nothing.
• A difference with the post I mentioned is the RX packets with errors I have, is this a clue of the problem?

Any help would be appreciated, Thanks!