Ubuntu – Can’t connect to ethernet with Atheros AR8161 on Ubuntu 12.04.2

I have read most of the answers that seem relevant to this, but I thinlk my issue is different and I haven't found the answer.

I have a new HP Pavilion HPE h8-1360t computer. It has Windows 7 and Ubuntu 12.04.2 in a dual boot configuration. It has a Ralink corp. RT5390 Wireless 802.11n wifi controller and an Atheros Communications Inc. AR8161 ethernet controller. I have two Lynksys WRT160N routers connected to different WANs and using DHCP for LAN client conmnections.

In Windows I can connect to the routers via WiFi and via wired ethernet. In Ubuntu, I can connect fine via WiFi, but ethernet connections 'try' for a while and then give 'wired network disconnected'.

It appears I have the required driver and sudo modprobe alx executes without error, but I can never establish a wired ethernet connection.

$ lspci | grep ^0[34]
03:00.0 Network controller: Ralink corp. RT5390 Wireless 802.11n 1T/1R PCIe
04:00.0 Ethernet controller: Atheros Communications Inc. AR8161 Gigabit Ethernet (rev 08)


$ sudo lshw -C network
  *-network               
       description: Wireless interface
       product: RT5390 Wireless 802.11n 1T/1R PCIe
       vendor: Ralink corp.
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: wlan0
       version: 00
       serial: 20:10:7a:89:4d:ef
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=rt2800pci driverversion=3.5.0-27-generic firmware=0.34 ip=192.168.1.158 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn
       resources: irq:16 memory:f7200000-f720ffff
  *-network
       description: Ethernet interface
       product: AR8161 Gigabit Ethernet
       vendor: Atheros Communications Inc.
       physical id: 0
       bus info: pci@0000:04:00.0
       logical name: eth0
       version: 08
       serial: 70:54:d2:97:05:11
       size: 100Mbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi msix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=alx driverversion=1.2.3 duplex=full firmware=N/A latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s
       resources: irq:17 memory:f7100000-f713ffff ioport:d000(size=128)


$ ifconfig
eth0      Link encap:Ethernet  HWaddr 70:54:d2:97:05:11  
          inet6 addr: fe80::7254:d2ff:fe97:511/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:306 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1617 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:174710 (174.7 KB)  TX bytes:335752 (335.7 KB)
          Interrupt:17 

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:1401 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1401 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:112404 (112.4 KB)  TX bytes:112404 (112.4 KB)

wlan0     Link encap:Ethernet  HWaddr 20:10:7a:89:4d:ef  
          inet addr:192.168.1.158  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::2210:7aff:fe89:4def/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7621 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6083 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3181961 (3.1 MB)  TX bytes:911510 (911.5 KB)

It seems that eth0 is up and that there is some communication, but I still get the 'wired network disconnected' alerts every minute or so and don't ever get connected.

Also it seems that if this were some DHCP protocol issue, the WiFi connection to the same router wouldn't work either.

I am lost. Can anyone help?